To date, PEHPL Program students have published 28 peer reviewed articles and more are on the way. Learn more about them below.
Diagnosis Challenges and Control Strategies of Transboundary Diseases Presenting with Respiratory Signs in Small Ruminants in Developing Countries: Emphasis on Contagious Caprine Pleuropneumonia and Peste Des Petits Ruminants
International Journal of Tropical Disease and Health 2020 41(22): 12-25
Methodology: A comprehensive review was carried out following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A total of 506 articles, handbooks, Master’s and PhD thesis and conference proceedings were collected and after removal of the duplicates 80.6% (424/526) passed the first stage. Of the remaining search materials, (n=291) were removed including handbooks, master’s and PhD thesis which did not originate from the developing countries, 31.4% (133/424) passed the second. Of the articles that passed the second stage, (n=85) were removed from the study, these included all articles that did not involve field diagnosis such as review papers and those not originating from the developing countries, 36.1% (48/133) passed the third stage. In the fourth stage, (n=5) articles which reported on retrospective cases and archived samples were removed and 43 articles were reviewed.
Results: Out of the 526 documents retrieved, 43 were eligible for review as they met all criteria for inclusion. Control strategies were recommended in 44.2% (19/43) of the articles of which most of them 63.2%, 12/19) recommended vaccination as a control strategy. Most of the articles reported definitive diagnosis reached following laboratory involvement as majority of them involved outbreak investigation or research works which is not the case in routine diagnosis. The major clinical signs mentioned in the review articles including fever 60.9% (14/23), oculonasal discharge 87.0% (20/23), respiratory distress 82.6% (19/23), erosive stomatitis 43.5% (10/23), diarrhea 56.5% (13/23) and coughing 30.4% (7/23) have been discussed relating to the definitive diagnosis reached in reporting articles. On the other hand, postmortem lesions including lung consolidation 38.1% (8/21), intestinal hemorrhage 38.1% (8/21), lung congestion 28.6% (6/21), serofibrinous pleurisy 28.6% (6/21), pneumonic lungs 23.8% (5/21) and unilateral lung inflammation 14.3% (3/21), have been discussed in relation to the definitive diagnosis reached.
Conclusion: Despite the similarities in clinical signs and postmortem lesions associated with diseases presenting with respiratory signs, definitive diagnosis of CCPP was reached in cases that involved clinical signs and postmortem lesions confined in the respiratory system whereas, PPR was more diagnosed in cases that presented with clinical signs and postmortem lesions associating the digestive system. However, presence of respiratory signs in the cases the diagnosed PPR may implicate presence of unidentified secondary bacterial infections. Vaccinations being the most advocated approach of control, require a broader look to make sure that polyvalent vaccines are available against the four common diseases. Also, use of treatment to reduce the effect of secondary infecting bacteria may be of help. Furthermore, for effective outcomes of the control strategies, collaborative efforts among countries at risk should be advocated.
Peste des petits ruminants Virus Transmission Scaling and Husbandry Practices That Contribute to Increased Transmission Risk: An Investigation among Sheep, Goats, and Cattle in Northern Tanzania
CM Herzog, WA de Glanville, BJ Willett, IM Cattadori, V Kapur, PJ Hudson, J Buza, ES Swai, S Cleaveland, and ON Bjørnstad
Viruses 2020 12(9): 930
Peste des petits ruminants virus (PPRV) causes an infectious disease of high morbidity and mortality among sheep and goats which impacts millions of livestock keepers globally. PPRV transmission risk varies by production system, but a deeper understanding of how transmission scales in these systems and which husbandry practices impact risk is needed. To investigate transmission scaling and husbandry practice-associated risk, this study combined 395 household questionnaires with over 7115 cross-sectional serosurvey samples collected in Tanzania among agropastoral and pastoral households managing sheep, goats, or cattle (most managed all three, n = 284, 71.9%). Although self-reported compound-level herd size was significantly larger in pastoral than agropastoral households, the data show no evidence that household herd force of infection (FOI, per capita infection rate of susceptible hosts) increased with herd size. Seroprevalence and FOI patterns observed at the sub-village level showed significant spatial variation in FOI. Univariate analyses showed that household herd FOI was significantly higher when households reported seasonal grazing camp attendance, cattle or goat introduction to the compound, death, sale, or giving away of animals in the past 12 months, when cattle were grazed separately from sheep and goats, and when the household also managed dogs or donkeys. Multivariable analyses revealed that species, production system type, and goat or sheep introduction or seasonal grazing camp attendance, cattle or goat death or sales, or goats given away in the past 12 months significantly increased odds of seroconversion, whereas managing pigs or cattle attending seasonal grazing camps had significantly lower odds of seroconversion. Further research should investigate specific husbandry practices across production systems in other countries and in systems that include additional atypical host species to broaden understanding of PPRV transmission.
Occurrence of Foot-and-Mouth Disease Virus Serotypes in Uganda and Tanzania (2003 to 2015): A Review and Implications for Prospective Regional Disease Control
SD Kerfua, MT Dhikusooka, AL Mulondo, J Bugeza, F Kabi, G Shirima, L Kusiluka, C Ayebazibwe, S Cleaveland, DT Haydon
Journal of Agricultural Science 2020 12(6)
Endemic foot-and-mouth disease (FMD) presents a global economic challenge to the livestock industry. The progressive control pathway for FMD (PCP-FMD) specifies successive steps through which a country/region can reduce FMD virus circulation and impact. These steps are reliant on understanding and obtaining knowledge on FMD epidemiology, to inform development of appropriate disease interventions like vaccination and quarantine programs. Currently, Uganda and Tanzania are in the early stages of the PCP-FMD. This review was undertaken to determine FMDV serotype distribution in Uganda and Tanzania between 2003 and 2015. The paper also presents the vaccine strains used in both countries for the same period viz avis the circulating topotypes. The review highlights four (O, A, SAT 1 and SAT 2) and five (O, A, SAT 1, SAT 2 and SAT 3) serotypes that occurred in Uganda and Tanzania respectively in the thirteen year period. Observations revealed that reported circulating serotypes O and A in the two countries belonged to similar topotypes, East African 2 (EA-2) and AFRICA respectively. The SAT 1 viruses in Tanzania belonged to topotype I and differed from the Ugandan SAT 1s that belonged to topotype IV. Similarly, the SAT 2s in both countries belonged to different topotypes: IV in Tanzania and I in Uganda. This review additionally, underscores the spatial distribution of FMDV serotypes in Uganda and Tanzania and highlights regions in both countries that had high serotype diversity. The paper recommends definitive disease diagnoses, molecular serotype characterisation and matched vaccination deployment for improved disease control.
Identifying Age Cohorts Responsible for Peste Des Petits Ruminants Virus Transmission among Sheep, Goats, and Cattle in Northern Tanzania
CM Herzog, WA de Glanville, BJ Willett, IM Cattadori, V Kapur, PJ Hudson, J Buza, ES Swai, S Cleaveland, and ON Bjørnstad
Viruses 2020 12(2): 186
Peste des petits ruminants virus (PPRV) causes a contagious disease of high morbidity and mortality in global sheep and goat populations. To better control this disease and inform eradication strategies, an improved understanding of how PPRV transmission risk varies by age is needed. Our study used a piece-wise catalytic model to estimate the age-specific force of infection (FOI, per capita infection rate of susceptible hosts) among sheep, goats, and cattle from a cross-sectional serosurvey dataset collected in 2016 in Tanzania. Apparent seroprevalence increased with age, reaching 53.6%, 46.8%, and 11.6% (true seroprevalence: 52.7%, 52.8%, 39.2%) for sheep, goats, and cattle, respectively. Seroprevalence was significantly higher among pastoral animals than agropastoral animals across all ages, with pastoral sheep and goat seroprevalence approaching 70% and 80%, respectively, suggesting pastoral endemicity. The best fitting piece-wise catalytic models merged age groups: two for sheep, three for goats, and four for cattle. The signal of these age heterogeneities were weak, except for a significant FOI peak among 2.5–3.5-year-old pastoral cattle. The subtle age-specific heterogeneities identified in this study suggest that targeting control efforts by age may not be as effective as targeting by other risk factors, such as production system type. Further research should investigate how specific husbandry practices affect PPRV transmission.
Association of LEI0258 Marker Alleles and Susceptibility to Virulent Newcastle Disease Virus Infection in Kuroiler, Sasso, and Local Tanzanian Chicken Embryos
FN Mpenda, CK Timabo, M Kyallo, J Juma, R Pelle, SL Lyantagaye, J Buza
Journal of Pathogens 2020: 1-8
Immune response following Newcastle disease
immunization and growth performance of kuroiler,
broiler and local Tanzanian chickens
FN Mpenda, SL Lyantagaye, J Buza
International Journal of Livestock Production 2020: 11(1): 1-7
Chicken is a major livestock species raised by smallholder households in rural areas in developing countries of Sub-Saharan Africa as a chief source of meat protein and income generation. However, Newcastle disease largely compromises the production of this precious bird under backyard production settings. The purpose of the study was to assess antibody responses and growth
performance following Newcastle disease vaccination in kuroiler, broiler, and local Tanzanian chickens raised under the same tropical environmental condition. In the experiment, a total of 358 chickens comprised of 127 kuroilers, 121 broilers, and 110 local Tanzanian chickens were raised for seven weeks, and body weights were recorded weekly. Birds were vaccinated at four weeks, and blood samples were collected at days 10, and 21 post-vaccination for antibody titres quantification by ELISA test. Results demonstrated higher (P < 0.05) antibody titres in kuroilers (3.81 ± 0.06) as compared to local chicken (3.73 ± 0.07) and broilers (3.53±0.06) at day 10 post-vaccination. The growth performance of local Tanzanian chickens was comparable to that of kuroilers. The present findings contribute to on-going work in understanding chicken immune responses against NDV and inform breeding programs designed for developing chickens with increased resistance to NDV.
Association of Chicken Mx1 Polymorphisms with Susceptibility in Chicken Embryos Challenged with Virulent Newcastle Disease Virus
FN Mpenda, SL Lyantagaye, J Buza
Asian Journal of Animal Sciences 2020: 14: 9-15
Background and Objective: Genetic selection of chicken genotypes that are less susceptible to Newcastle disease virus (NDV) is a
promising option. The present study aimed to investigate polymorphism of chicken Mx1 gene G2032A SNP in different chicken
breeds in Tanzania and association with chicken embryos susceptibility to virulent NDV. Materials and Methods: A total of 355
(87 Sasso, 129 Kuroiler and 139 local) 16 days old chicken embryos were infected with 0.1 mL minimum lethal dose (103
/0.1 mL) of virulent NDV suspension. The time of death was recorded and selective genotyping was deployed where chicken embryos from high (15%) and less (15%) susceptible cohorts were genotyped by PCR-length polymorphism. Two forward and a reverse primers were used to generate 2 different sizes of PCR product of A and G alleles of chicken Mx1 gene G2032A SNP. Results: As expected chicken embryos survival was highly variable within a breed. The frequency of allele A was higher than allele G in chicken breeds. Furthermore, using Pearsonʼs X2 test of independence, it was demonstrated that chicken Mx1 gene G2032A genotypes (AA, AG and GG) were associated (p<0.05) with chicken embryos susceptibility to virulent NDV infection. The frequency of genotype AA was higher in less susceptible chicken embryos, whereas, frequency of genotype GG and AG was higher in high susceptible chicken embryos. Conclusion: Results from the present study provide valuable information on the potential role of Mx1 gene polymorphism for selection of chickens that are resistant to virulent NDV infection.
Polymorphisms of the Chicken Mx Gene Promoter and
Association with Chicken Embryos’ Susceptibility to VirulenT Newcastle Disease Virus Challenge
FN Mpenda, CT Keambou, M Kyallo, R Pelle, SL Lyantagaye, J Buza
Biomedical Research International 2019
Newcastle disease is a devastating viral disease of chicken in low- and middle-income countries where the backyard production
system is predominant. Marker-assisted selection of chickens that are resistant to Newcastle disease virus (NDV) is the promising
strategy that needs to be explored. Te aim of the present study was to investigate polymorphisms of the promoter region of the
chicken Mx gene and association with Kuroiler, Sasso, and local Tanzanian chicken embryos’ survival variability to virulent NDV
infection. Chicken embryos were initially challenged with a minimum lethal dose of virulent NDV suspension and then were
followed over time to gather information on their survival variability. Using the survival data, high and less susceptible cohorts
were established, and a total of 88 DNA samples from high and less susceptible groups were genotypes by sequencing. Five single-
nucleotide polymorphisms (SNPs), which were previously reported, were detected. Interestingly, for the frst time, the fndings
demonstrated the association of the promoter region of chicken myxovirus-resistance (Mx) gene polymorphisms with chicken
embryos’ susceptibility to the virulent NDV challenge. At the genotypic level, the SNP4 G>A mutation that was located within the
IFN-stimulating response element was associated (LR: 6.97, P ! 0.03) with chicken embryos’ susceptibility to the virulent NDV
challenge. An allele G frequency was higher in the less susceptible cohort, whereas an allele A frequency was higher in the high
susceptible cohort. At the haplotype level, the haplotype group ACGC was associated (OR: 9.8, 95% CI: 1.06–79.43, P ! 0.042)
with the same trait and had a resistant efect. In conclusion, the results have demonstrated the association of chicken Mx gene
promoter polymorphisms and chicken embryos’ survival variability to the virulent NDV challenge, and the information is useful
for breeding programs designed to develop chicken genotypes that are resistant to Newcastle disease virus.
The genetic diversity of local african chickens: a potential for selection of chickens resistant to viral infections
FN Mpenda, MA Schilling, Z Campbell, EB Mngumi, J Buza
Journal of Applied Poultry Research 2019: 28: 1-12
Viral infections impose a great threat to backyard chicken production among poor rural households in developing countries. These infections limit the contribution of chicken production in improving the livelihoods of poor communities, particularly in Africa. Chicken viral infections lack treatment options; control and prevention depend primarily on adoption of vaccines and good farm management practice such as the institution of biosecurity measures. In backyard production systems, these control options are less practical and less feasible to implement. Research has demonstrated the role of genetic diversity of farmed animals and birds in
explaining variation in resistance to infectious diseases and suggests that heterogeneous populations are less susceptible to disease than homogeneous populations. Local African chicken ecotypes have high genetic diversity and have demonstrated the ability to survive persistent exposure to pathogens and harsh environmental conditions. This suggests that local African chickens have the genetic potential to enhance breeding strategies for resistance to viral infections. Despite the ongoing threat of infectious disease and dynamic of diseases epidemiology attributed by climate change, little has been done to harness the genetic potential of local
African chicken ecotypes to breed for resistant traits. To lay the foundation for future research, this review paper presents a summary of challenges facing current chicken viral infections control and prevention options in local African chickens, and gives an overview of documented information on the genetic diversity and population structure of local African chicken ecotypes.
Newcastle disease (ND) control by vaccination and an institution of biosecurity measures is less feasible in backyard chicken in developing countries. *erefore, an alternative disease control strategy like the genetic selection of less susceptible chicken genotypes is a promising option. In the present study, genetic polymorphism of LEIO258 marker and association with susceptibility to virulent Newcastle disease virus (NDV) infection in Kuroilers, Sasso, and local Tanzanian chicken embryos were investigated. Samples from high (15%) and less (15%) susceptible cohorts were genotyped by sequencing of LEI0258 marker. A total of 75 DNA sequences comprised of 29 Kuroiler, 29 local Tanzanian chickens, and 17 Sasso were analyzed. Neighbor-joining phylogenetic trees were constructed to depict the clustering of LEI0258 marker alleles and relationship with susceptibility. Alleles with frequency ≥3 were considered for association with susceptibility by the use of the inference technique. *e present findings suggest that some LEI0258 marker genetic polymorphisms apart from LEI0258 marker allelic based on sizes may be linked with chicken MHC-B haplotypes that confer chickens variability in resistance or susceptibility to infections. Furthermore, these results demonstrate the presence of relationship between LEI0258 marker polymorphisms and variations in chicken susceptibility to NDV infection, which could be utilized in breeding programs designed to improve chicken disease resistance.
Enhancing livestock vaccination decision-making through rapid diagnostic testing
AF Railey, F Lankester, T Lembo, R Reeve, G Shirima, and TL Marsh
World Development Perspectives 2019: 16: 100144
• Compared to vaccination, the collective approach to diagnostic testing presents a low-fixed cost.
• Existing household livestock-health behaviors increase the likelihood for uptake of preventative health practices.
• Initial evidence to support household investments in livestock preventative health over therapeutic treatments.
Machine learning models for predicting the use of different animal breeding services in smallholder dairy farms in Sub-Saharan Africa
G Mwanga, S Lockwood, DFN Mujibi, Z Yonah, MGG Chagunda
Tropical Animal Health and Production 2019: 1-11
This study is concerned with developing predictive models using machine learning techniques to be used in identifying factors that influence farmers’ decisions, predict farmers’ decisions, and forecast farmers’ demands relating to breeding service. The data used to develop the models comes from a survey of small-scale dairy farmers from Tanzania (n = 3500 farmers), Kenya (n = 6190 farmers), Ethiopia (n = 4920 farmers), and Uganda (n = 5390 farmers) and more than 120 variables were identified to influence breeding decisions. Feature engineering process was used to reduce the number of variables to a practical level and to identify the most influential ones. Three algorithms were used for feature selection, namely: logistic regression, random forest, and Boruta. Subsequently, six predictive models, using features selected by feature selection method, were tested for each country—neural network, logistic regression, K-nearest neighbor, decision tree, random forest, and Gaussian mixture model. A combination of decision tree and random forest algorithms was used to develop the final models. Each country model showed high predictive power (up to 93%) and are ready for practical use. The use of ML techniques assisted in identifying the key factors that influence the adoption of breeding method that can be taken and prioritized to improve the dairy sector among countries. Moreover, it provided various alternatives for policymakers to compare the consequences of different courses of action which can assist in determining which alternative at any particular choice point had a high probability to succeed, given the information and alternatives pertinent to the breeding decision. Also, through the use of ML, results to the identification of different clusters of farmers, who were classified based on their farm, and farmers’ characteristics, i.e., farm location, feeding system, animal husbandry practices, etc. This information had significant value to decision-makers in finding the appropriate intervention for a particular cluster of farmers. In the future, such predictive models will assist decision-makers in planning and managing resources by allocating breeding services and capabilities where they would be most in demand.
A Rational Explanation of Limited FMD Vaccine Uptake in Endemic Regions
AF Railey and TL Marsh
Pathogens 2019: 8(4):181
Vaccination for foot-and-mouth (FMD) disease remains low in parts of Africa despite the existence of vaccines. In East Africa, the presence of multiple virus serotypes and sub-types makes matching a vaccine with the circulating virus type in the field, or providing a high potency vaccine, a challenge. In this paper we use game theory to show that the resulting vaccine uncertainty associated with these vaccination conditions in an endemic setting help explain the low vaccine uptake. We evaluate vaccination for FMD in the context of East Africa due to FMD being endemic in the region, the diversity of FMD virus types, and barriers to implementing other disease control measures, such as controlled movements. We incorporate these conditions into a vaccination game setting and compare the payoffs to those of a traditional vaccination game for seasonal influenza and commercial livestock vaccination in a developed country context. In showing that vaccination provides households with a lower payoff than not vaccinating, our simple game theoretical explanation supports existing evidence calling for improved vaccine quality and efforts to enhance surveillance to provide early information on disease status.
Why isn’t everyone using the thermotolerant vaccine? Preferences for Newcastle disease vaccines by chicken-owning households in Tanzania
ZA Campbell, SM Thumbi, TL Marsh, MB Quinlan, GM Shirima, GH Palmer
PLOS ONE 2019: 14(8): e0220963
Understanding preferences for veterinary vaccines in low and middle-income countries is important for increasing vaccination coverage against infectious diseases, especially when the consumer is responsible for choosing between similar vaccines. Over-the-counter sales of vaccines without a prescription gives decision-making power to consumers who may value vaccine traits differently from national or international experts and vaccine producers and distributers. We examine consumer preferences for La Sota and I-2 Newcastle disease vaccines in Tanzania to understand why two vaccines co-exist in the market when I-2 is considered technically superior because of its thermotolerance. Household survey and focus group results indicate consumers perceive both vaccines to be effective, use the two vaccines interchangeably when the preferred vaccine is unavailable, and base preferences more on administration style than thermotolerance. Considering the consumers’ perspectives provides a way to increase vaccination coverage by targeting users with a vaccine that fits their preferences.
Farmer-preferred traits in smallholder dairy farming systems in Tanzania
AR Chawala, G Banos, A Peters, MGG Chagunda
Tropical Animal Health and Production 2019, 51(6): 1337–1344
Decisions of breeding schemes in many countries in sub-Saharan Africa tend to be either government or project driven, with a focus on upgrading local breeds. However, there is scant information on the individual animal traits that smallholder farmers prefer. The aim of this study was to examine farmers’ preferences of dairy cattle traits using a discrete choice experiment methodology. The study was conducted through visits to 555 randomly selected dairy farms in the sub-humid Eastern coast and temperate Southern highlands of Tanzania. Choices of animal traits were presented to farmers who were asked to evaluate choice alternatives based on attribute levels and finally select the alternative with the highest utility. The choice experiment data were analysed using a conditional logit model. Coefficients for milk yield, fertility, feed requirement, temperament and diseases resistance were overall statistically significant (p < 0.05). In order of perceived importance, farmers were willing to keep a cow with high milk yield (coefficient = 1.43 ± 0.059), good fertility (0.85 ± 0.050), easy temperament (0.76 ± 0.066), low feed requirement (− 0.56 ± 0.092) and enhanced tropical disease resistance (0.48 ± 0.048). The purchase price coefficient was negative (− 0.001 ± 0.0003), indicating that farmers would prefer improved dairy cattle at affordable prices. Farmers’ preferred traits were influenced by agro-ecological zone and type of production system (extensive vs intensive). The study provides an opportunity for breeding programme designers to take farmers’ preferred dairy traits into serious consideration.
Pastoral production is associated with increased peste des petits ruminants seroprevalence in northern Tanzania across sheep, goats and cattle
CM Herzog, WA de Glanville, BJ Willett, TJ Kibona, IM Cattadori, V Kapur, PJ Hudson, J Buza, S Cleaveland, and ON Bjørnstad
Epidemiology and Infection 2019: 147: e242
Peste des petits ruminants virus (PPRV) causes a contagious disease of high morbidity and mortality in small ruminant populations globally. Using cross-sectional serosurvey data collected in 2016, our study investigated PPRV seroprevalence and risk factors among sheep, goats and cattle in 20 agropastoral (AP) and pastoral (P) villages in northern Tanzania. Overall observed seroprevalence was 21.1% (95% exact confidence interval (CI) 20.1–22.0) with 5.8% seroprevalence among agropastoral (95% CI 5.0–6.7) and 30.7% among pastoral villages (95% CI 29.3–32.0). Seropositivity varied significantly by management (production) system. Our study applied the catalytic framework to estimate the force of infection. The associated reproductive numbers (R0) were estimated at 1.36 (95% CI 1.32–1.39), 1.40 (95% CI 1.37–1.44) and 1.13 (95% CI 1.11–1.14) for sheep, goats and cattle, respectively. For sheep and goats, these R0 values are likely underestimates due to infection-associated mortality. Spatial heterogeneity in risk among pairs of species across 20 villages was significantly positively correlated (R2: 0.59–0.69), suggesting either cross-species transmission or common, external risk factors affecting all species. The non-negligible seroconversion in cattle may represent spillover or cattle-to-cattle transmission and must be investigated further to understand the role of cattle in PPRV transmission ahead of upcoming eradication efforts.
Risk factors associated with Mycoplasma capricolum subspecies capripneumoniae and morbillivirus infection in small ruminants in Tanzania
A Chota, G Shirima, L Kusiluka
Tropical Animal Health and Production 2019: 51(7):1807–1815
Mortality of domestic small ruminants caused by contagious caprine pleuropneumonia (CCPP) and Peste des petits ruminants (PPR) is frequently reported in Tanzania. A cross-sectional survey was conducted between June, 2016 and July, 2017 to identify risk factors for small ruminants exposure to Mycoplasma capricolum subsp. capripneumoniae (M. capripneumoniae), the causative agent of CCPP, and small ruminant morbillivirus (SRMV), the causative agent of PPR. Antibody detection was done using competitive enzyme-linked immunosorbent assays (cELISA); similarly, a semi-structured questionnaire was administered in flocks where serum samples were collected. Individual seropositivity for M. capripneumoniae was 6.5% (n = 676) and 4.2% (n = 285) in goats and sheep respectively, whereas SRMV was 28.6% in goats (n = 676) and 31.9% in sheep (n = 285). Multivariable analysis indicated that mixing of flocks was a risk factor for exposure to M. capripneumoniae (χ2 = 3.9, df = 1, p = 0.05) and SRMV (χ2 = 6.3, df = 1, p = 0.01) in goats. Age was a protective factor for SRMV seropositivity in both goats (χ2 = 7.4, df = 1, p = 0.006) and sheep (χ2 = 10.2, df = 1, p = 0.006). SRMV seropositivity in goats was also influenced by grazing in contact with wild animals (χ2 = 5.9, df = 1, p = 0.02) and taking animals to the animal markets (χ2 = 8.2, df = 1, p = 0.004). M. capripneumoniae and SRMV are influenced by several risk factors and their control needs concerted efforts between stakeholders, which may include community involvement in mandatory vaccination and animals’ movement control.
Innate Immune Genes Associated With Newcastle Disease Virus Load in Chick Embryos From Inbred and Outbred Lines
MA Schilling, S Memari, IM Cattadori, R Katani, AP Muhairwa, JJ Buza, and V Kapur
Frontiers in Microbiology 2019: 10:143
Newcastle disease virus (NDV) causes substantial economic losses to smallholder farmers in low- and middle-income countries with high levels of morbidity and mortality in poultry flocks. Previous investigations have suggested differing levels of susceptibility to NDV between specific inbred lines and amongst breeds of chickens, however, the mechanisms contributing to this remain poorly understood. Studies have shown that some of these differences in levels of susceptibility to NDV infection may be accounted for by variability in the innate immune response amongst various breeds of poultry to NDV infection. Recent studies, in inbred Fayoumi and Leghorn lines, uncovered conserved, breed-dependent, and subline-dependent responses. To better understand the role of innate immune genes in engendering a protective immune response, we assessed the transcriptional responses to NDV of three highly outbred Tanzanian local chicken ecotypes, the Kuchi, the Morogoro Medium, and the Ching’wekwe. Hierarchical clustering and principal coordinate analysis of the gene expression profiles of 21-day old chick embryos infected with NDV clustered in an ecotype-dependent manner and was consistent with the relative viral loads for each of the three ecotypes. The Kuchi and Morogoro Medium exhibit significantly higher viral loads than the Ching’wekwe. The results show that the outbred ecotypes with increased levels of expression of CCL4, NOS2, and SOCS1 also had higher viral loads. The higher expression of SOCS1 is inconsistent with the expression in inbred lines. These differences may uncover new mechanisms or pathways in these populations that may have otherwise been overlooked when examining the response in highly inbred lines. Taken together, our findings provide insights on the specific conserved and differentially expressed innate immune-related genes involved the response of highly outbred chicken lines to NDV. This also suggests that several of the specific innate immunity related genes identified in the current investigation may serve as markers for the selection of chickens with reduced susceptibility to NDV.
Influence of Seasonal Cattle Movement on Prevalence of Trypanosome Infections in Cattle in the Maasai Steppe, Tanzania
K Ngongolo, AB Estes, PJ Hudson, and PS Gwakisa
Journal of Infectious Diseases and Epidemiology 2019: 5:079.
Animal African Trypanosomosis is a Neglected Tropical Disease with significant impacts to pastoral community livelihoods. Our study sought to determine the influence of seasonal cattle movements on the prevalence of trypanosome infections in cattle in the pastoral areas of the Maasai Steppe. Identification of spatial and temporal dynamics of trypanosome infections in cattle is essential for designing effective control strategies. To identify potential hotspots of trypanosome transmission, we worked with 5 pastoralists in each of 3 villages in the Maasai Steppe of northern Tanzania, and consecutively sampled 10 of each of their cattle in 3 periods, covering both wet and dry season grazing ranges (July 2017 to January 2018). Each time blood was collected from the cattle, a prophylactic dose of diminazene aceturate was administered to clear any parasites acquired in the previous 3 months. We then used participatory mapping techniques to identify the areas where the pastoralists had grazed their herds since the last sampling period, and interviewed them about any disease control methods they practice. Trypanosome infections in the sampled cattle blood were detected using nested polymerase chain reaction with ITS-1 primers. The overall prevalence of trypanosome infections across all sample periods and villages was 12%, though this varied distinctly by season and grazing area. Prevalence in July 2017 (19.33%) was significantly higher than prevalence in October 2017 (2%) (p < 0.05). A total of 45 grazing areas were identified and cattle acquired trypanosome infections in almost half of these (n = 21). Targeted awareness on seasonality and hotspot areas of trypanosome infections will help Maasai pastoralists to plan movement of their cattle strategically to avoid disease risk. These results also suggest enhanced control strategies for Trypanosomosis during the months of the year when cattle are moved further from homesteads to graze in hot spot areas.
Assessing Risk Factors for Trypanosome Infections in Cattle in Wildlife Interface Areas in Northern Tanzania
K Ngongolo, AB Estes, PJ Hudson, and PS Gwakisa
Journal of Infectious Diseases and Epidemiology 2019: 5:078.
Trypanosomosis is a vector-borne, tropical disease that causes mortality and morbidity in livestock and humans. In this study we investigated the risk factors for trypanosome infection in cattle in the Maasai Steppe of northern Tanzania. We assessed the influence of age, sex, herd size and history of treatment against trypanosomosis as risk factors of trypanosome infection. Cattle blood samples were collected from 150 cattle in three villages in the vicinity of Tarangire National Park, which acts as a reservoir of tsetse flies, the trypanosome vector. Parasite species were identified using a nested Polymerase Chain Reaction (n-PCR). Smaller herd sizes, young age (1-2 years), and male sex significantly increased the risk of trypanosome infections. Efforts to control trypanosome infection should be strategically based on location and season while considering age, treatment and herd size as risk factors.
Conserved, breed-dependent, and subline-dependent innate immune responses of Fayoumi and Leghorn chicken embryos to Newcastle disease virus infection
MA Schilling, S Memari, M Cavanaugh, R Katani, MS Deist, J Radzio-Basu, SJ Lamont, J Buza, and V Kapur
Nature Scientific Reports 2019: 9, 7209.
Newcastle disease virus (NDV) is a threat to the global poultry industry, but particularly for smallholder farmers in low- and middle-income countries. Previous reports suggest that some breeds of chickens are less susceptible to NDV infection, however, the mechanisms contributing to this are unknown. We here examined the comparative transcriptional responses of innate immune genes to NDV infection in inbred sublines of the Fayoumi and Leghorn breeds known to differ in their relative susceptibility to infection as well as at the microchromosome bearing the major histocompatability complex (MHC) locus. The analysis identified a set of five core genes, Mx1, IRF1, IRF7, STAT1, and SOCS1, that are up-regulated regardless of subline. Several genes were differentially expressed in a breed- or subline-dependent manner. The breed-dependent response involved TLR3, NOS2, LITAF, and IFIH1 in the Fayoumi versus IL8, CAMP, and CCL4 in the Leghorn. Further analysis identified subline-dependent differences in the pro-inflammatory response within the Fayoumi breed that are likely influenced by the MHC. These results have identified conserved, breed-dependent, and subline-dependent innate immune responses to NDV infection in chickens, and provide a strong framework for the future characterization of the specific roles of genes and pathways that influence the susceptibility of chickens to NDV infection.
Low topotype diversity of recent foot-and-mouth disease virus serotypes O and A from districts located along the Uganda and Tanzania border
SD Kerfua, G Shirima, L Kusiluka, C Ayebazibwe, E Martin, E Arinaitwe, S Cleaveland, and DT Haydon
Journal of Veterinary Science 2019, 20(2):e4
Foot-and-mouth disease (FMD) is one of the most important livestock diseases in East Africa with outbreaks reported annually that cause severe economic losses. It is possible to control disease using vaccination, but antigenic matching of the vaccine to circulating strains is critical. To determine the relationship between foot-and-mouth disease viruses circulating in districts along the Uganda and Tanzanian border between 2016 and 2017 and currently used vaccines, phylogenetic analysis of the full VP1 virus sequences was carried out on samples collected from both sides of the border. A total of 43 clinical samples were collected from animals exhibiting signs of FMD and VP1 sequences generated from 11 of them. Eight out of the 11 sequences obtained belonged to serotype O and three belonged to serotype A. The serotype O sequences obtained showed limited nucleotide divergence (average of 4.9%) and belonged to topotype East Africa-2, whereas the most common O-type vaccine strain used in the region (O/KEN/77/78) belonged to East Africa-1. The serotype A viruses belonged to topotype Africa-G1 (average nucleotide divergence 7.4%), as did vaccine strain K5/1980. However, vaccine strain K35/1980 belonged to Africa G VII with an average sequence divergence of 20.5% from the study sequences. The genetic distances between current vaccine strains and circulating field strains underscores the crucial need for regular vaccine matching and the importance of collaborative efforts for better control of FMD along this border area.
Drivers of vaccination preferences to protect a low-value livestock resource: Willingness to pay for Newcastle disease vaccines by smallholder households
ZA Campbell, L Otieno, GM Shirima, TL Marsh, GH Palmer
Vaccine 2019: 37(1): 11-18
Vaccination can be an effective risk management approach to minimize the burden of disease and increase livestock productivity for smallholder households in low income countries. In contrast to vaccination of cattle, a high-value smallholder asset, there is a significant knowledge gap for the drivers of vaccine adoption of smallholder poultry. Newcastle disease virus (NDV) causes high mortality in chickens and is one of the greatest constraints to East African poultry production. To determine preferences and willingness to pay for NDV vaccines by chicken-owning households in Tanzania, we administered a survey with a contingent valuation activity to 535 households across six villages in Arusha, Singida, and Mbeya regions. Given the low current vaccination rate, we tested the null hypothesis that smallholder households do not value NDV vaccines and found overwhelming evidence that smallholders do value NDV vaccines. The willingness to pay (WTP) estimate was 5853 Tanzanian shillings ($2.64) to vaccinate ten chickens given the vaccine was protective for a period of three months. This estimate is about twice the market price reported by households in the study areas suggesting chicken-owning households value and benefit from NDV vaccines, but face other barriers to vaccination. Previous vaccination had the largest positive effect size on WTP suggesting smallholders observe benefits from vaccinating. In contrast to studies of vaccination of higher-cost cattle where off-farm income sources often drive willingness to pay, on-farm income was a driver of WTP for NDV vaccines suggesting different drivers affect protection of low-value livestock assets as compared to high-value assets.
Newcastle disease vaccine adoption by smallholder households in Tanzania: Identifying determinants and barriers
ZA Campbell, TL Marsh, E Mpolya, SM Thumbi, GH Palmer
PLOS ONE 13(10): e0206058
Food security is critical to achieving sustainable growth, poverty reduction, and political and economic stability. Livestock have the potential to improve the food security of smallholder households in developing countries, but livestock productivity is constrained by disease. The extent to which households adopt innovations such as vaccines impacts disease control; however, the behavioral and economic drivers underlying household decisions to adopt or forgo vaccination are not well understood. We address this gap with a study of adoption of Newcastle disease (ND) vaccines by chicken-owning households in Tanzania. A cross-sectional survey was administered to 535 households owning indigenous chickens in Arusha, Singida, and Mbeya regions in Tanzania. We measured potential predictors of ND vaccine adoption including knowledge, attitudes, and practices. Logistic regression was used to identify predictors correlated with three stages of household adoption: awareness of ND vaccines, previous vaccination, and recent vaccination (within four months) consistent with veterinary guidelines. Eighty percent of households were aware of ND vaccines, 57% had previously vaccinated, and 26% had recently vaccinated. Knowing someone who vaccinated increased the odds of a household previously vaccinating [adjusted odds ratio (AOR): 1.32, 95% CI: 1.1–1.5]. Larger flock size was also associated with higher odds of previous vaccination (AOR: 1.03 for a one chicken increase, 95% CI: 1.01–1.05). Usage of traditional medicine decreased the odds of previously vaccination (AOR: 0.58, 95% CI: 0.36–0.95). Our findings suggest that encouraging the flow of professional-level knowledge within the community by vaccine adopters is a strategy to increase vaccine adoption. Enhancing local chicken productivity through increased vaccine coverage would strengthen a key smallholder household resource for food and economic security.
Multi-country investigation of factors influencing breeding decisions by smallholder dairy farmers in sub-Saharan Africa
G Mwanga, F Mujibi, Z Yonah, MGG Chagunda
Tropical Animal Health and Production 2018: 51(2): 395–409
Artificial insemination (AI) and selective bull mating are considered as robust methods for dairy cattle breeding. Globally, these methods have been used to enhance productivity and realize rapid genetic gains. However, these technologies have had low adoption rates in sub-Saharan Africa (SSA). Even though available evidence suggests that this is due to various infrastructural and technical challenges. There is limited information about what drives this low uptake of AI from a farmer’s perspective. Therefore, the main objective of this study was to determine and characterize factors that influence the choice by smallholder farmers between bull service and AI for dairy cow breeding. Further, the relationships between the breeding choices and the bio-physical elements of dairy farming, mainly, farmer characteris- tics, household income levels, farm management practices, and institutional support structures, were investigated. Data were collected through face-to-face interviews from a total of 16,308 small-scale dairy farmers in Ethiopia (n =4679), Kenya (n = 5278), Tanzania (n = 3500), and Uganda (n = 2851). The questionnaire was coded in an electronic form using Open Data Kit (ODK) platform to allow for real-time data entry and management. Descriptive statistics, chi-square test, and a t-test were used to evaluate the independent and dependent variables, while logistic regression and factor analysis were used to identify factors that influenced farmers’ breeding decisions. Results showed that there was a significant difference in animal husbandry practices between farmers who used artificial insemination (AI) and those who practiced bull mating. The majority of farmers who used AI kept records, purchased more animal feeds, had more labor by hiring workers whose average wages were higher than those of bull service farmers. However, farmers who used AI pay more for services such as water access and breeding while their service providers had to cover long distances compared to farmers who used bulls. This indicates limited access to services and service providers for AI farmers. The ratio of AI to bull service users was even for Ethiopia and Kenya, while in Uganda and Tanzania, more farmers preferred bull service to AI. It was established that the factors that influence farmers’ breeding decision were not the same across the region. Factors such as farmer’s experience in dairy farming, influence of the neighbor, farmer’s ability to keep records, and management practices such as water provision and availability of feeds had a significant association (p <0.001) with AI adoption among dairy farmers. In contrast, large herd and large land size negatively influenced AI adoption. Institutional settings including cost of AI service and the distance covered by the service provider negatively affected (p < 0.001) the choice of AI as a breeding option. There was a high probability of continued use of a specific breeding method when there was a previous conception success with that same method. Based on the results obtained, we recommend that improvement of institutional settings such as the availability of AI service providers, as well as better access to services such as water, animal feed, and animal health provision, be treated as critical components to focus on for enhanced AI adoption. Most importantly, there is a need to avail training opportunities to equip farmers with the necessary skills for best farm management practices such as record keeping, proper feeding, and selective breeding.
Spatial and temporal distribution of foot-and-mouth disease in four districts situated along the Uganda–Tanzania border: Implications for cross-border efforts in disease control
S Kerfua, G Shirima, L Kusiluka, C Ayebazibwe, R Mwebe, S Cleaveland, et al.
Onderstepoort J Vet Res. 2018;85(1):1–8.
Foot-and-mouth disease (FMD) is one of the major trans-boundary animal diseases in East Africa causing economic loss to farmers and other stakeholders in the livestock industry. Foot- and-mouth disease occurs widely in both Uganda and Tanzania with annual outbreaks recorded. With the recent introduction of the Progressive Control Pathway for FMD control (PCP-FMD) in eastern Africa, knowledge of the spatial and temporal distribution of FMD at the border area between Uganda and Tanzania is helpful in framing engagement with the initial stages of the PCP. Retrospective data collected between 2011 and 2016 from four districts located along the border areas of Uganda and Tanzania, recorded 23 and 59 FMD outbreaks, respectively, for the entire study period. Analysis showed that 46% of the 82 recorded outbreaks occurred in 20% of sub-counties and wards immediately neighbouring the Uganda–Tanzania border and 69.5% of the outbreaks occurred during the dry months. While the serotypes of the FMD virus responsible for most outbreaks reported in this region were not known, previous research reported South African Territory (SAT) 1, SAT 2 and O to be the serotypes in circulation. The results from this study provide evidence of the endemic status of FMD on the Uganda–Tanzania border and emphasise that the border area should be given due consideration during FMD control drives and that cross-border coordination should be prioritised. With the limited data on circulating serotypes in this area, there is a need for more vigilance on FMD case detection, laboratory diagnostic confirmation and provision of more complete documentation of outbreaks. This work further recommends more studies on cross-border livestock movement coupled with phylogenetics in order to understand the spread of the FMD in the border area.
Spatial and temporal risk as drivers for adoption of foot and mouth disease vaccination
AF Railey, T Lembo, GH Palmer, GM Shirima, TL Marsh
Identifying the drivers of vaccine adoption decisions under varying levels of perceived disease risk and benefit provides insight into what can limit or enhance vaccination uptake. To address the relationship of perceived benefit relative to temporal and spatial risk, we surveyed 432 pastoralist households in northern Tanzania on vaccination for foot-and-mouth disease (FMD). Unlike human health vaccination decisions where beliefs regarding adverse, personal health effects factor heavily into perceived risk, deci- sions for animal vaccination focus disproportionately on dynamic risks to animal productivity. We extended a commonly used stated preference survey methodology, willingness to pay, to elicit responses for a routine vaccination strategy applied biannually and an emergency strategy applied in reaction to spatially variable, hypothetical outbreaks. Our results show that households place a higher value on vaccination as perceived risk and household capacity to cope with resource constraints increase, but that the episodic and unpredictable spatial and temporal spread of FMD contributes to increased levels of uncer- tainty regarding the benefit of vaccination. In addition, concerns regarding the performance of the vac- cine underlie decisions for both routine and emergency vaccination, indicating a need for within community messaging and documentation of the household and population level benefits of FMD vaccination.
Transcriptional innate immune response of the developing chicken embryo to Newcastle disease virus infection
MA Schilling, R Katani, S Memari, M Cavanaugh, J Buza, JR Basu, et al.
Frontiers in Genetics 2018;9(FEB):1–9.
Traditional approaches to assess the immune response of chickens to infection are through animal trials, which are expensive, require enhanced biosecurity, compromise welfare, and are frequently influenced by confounding variables. Since the chicken embryo becomes immunocompetent prior to hatch, we here characterized the transcriptional response of selected innate immune genes to Newcastle disease virus (NDV) infection in chicken embryos at days 10, 14, and 18 of embryonic development. The results suggest that the innate immune response 72 h after challenge of 18-day chicken embryo is both consistent and robust. The expression of CCL5, Mx1, and TLR3 in lung tissues of NDV challenged chicken embryos from the outbred Kuroiler and Tanzanian local ecotype lines showed that their expression was several orders of magnitude higher in the Kuroiler than in the local ecotypes. Next, the expression patterns of three additional innate-immunity related genes, IL-8, IRF-1, and STAT1, were examined in the highly congenic Fayoumi (M5.1 and M15.2) and Leghorn (Ghs6 and Ghs13) sublines that differ only at the microchromosome bearing the major histocompatibility locus. The results show that the Ghs13 Leghorn subline had a consistently higher expression of all genes except IL-8 and expression seemed to be subline-dependent rather than breed-dependent, suggesting that the innate immune response of chicken embryos to NDV infection may be genetically controlled by the MHC-locus. Taken together, the results suggest that the chicken embryo may represent a promising model to studying the patterns and sources of variation of the avian innate immune response to infection with NDV and related pathogens.
Phenotypic and genetic parameters for selected production and reproduction traits of Mpwapwa cattle in low-input production systems
AR Chawala, G Banos , DM Komwihangilo, A Peters, MGG Chagunda
South African Journal of Animal Science 2017, 47 (No. 3)
The objective of this study was to assess the genetic improvement programme of the Mpwapwa dairy cattle breed over the past four decades, based on on-station selection and breeding. Estimates of genetic parameters and genetic trends for total lactation milk yield (LMY), 305-day lactation milk yield (305LMY), lactation length (LL), age at first calving (AFC), and calving interval (CI) were derived. The study used 1,003 lactation records from 385 cows and 78 sires collected from 1967 to 2012. Genetic parameters were estimated using an animal model procedure with ASReml software. The heritability for LMY and 305LMY were moderately high (0.33 ± 0.11–0.44 ± 0.04) and low for LL (0.13 ± 0.17.0). Repeatability for LMY and 305LMY was high (0.62 ± 0.04–0.70 ± 0.03) and moderate for LL (0.27 ± 0.06). The heritability for AFC (0.13 ± 0.11) and CI (0.10 ± 0.05) were low. The repeatability for CI was low (0.10 ± 0.05). Genetic correlation of 305LMY with LMY and CI were 0.87 ± 0.02 and -0.06 ± 0.009, respectively, while the corresponding phenotypic correlation estimates were 0.82 ± 0.01 and -0.01 ± 0.001. Variation among animal estimated breeding values (EBV) was significant, suggesting that selection to improve these traits is feasible. Thirty seven out of 78 sires had favourable EBV (0–900 kg) for milk yield, which suggests that selection for specific sires could result in increased LMY. Annual rates of sires EBV change for 305LMY, LL, CI, and AFC were -0.05, 0.15, and -0.14 days, respectively. All these traits showed that a decline in genetic progress for Mpwapwa dairy cattle in the on-station breeding programme.