Browsing by Author "Cook, Elizabeth"

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Brucella Species Circulating in Smallholder Dairy Cattle in Tanzania
(MDPI, 2024-09-21) Mengele, Isaac; Akoko, James; Shirima, Gabriel; Bwatota, Shedrack; Motto, Shabani; Hernandez-Castro, Luis; Komwihangilo, Daniel; Lyatuu, Eliamoni; de Clare Bronsvoort, Barend; Cook, Elizabeth
Brucellosis is a zoonosis caused by bacteria of the genus Brucella, which results in economic losses relating to livestock and threatens public health. A cross-sectional study was conducted to determine the molecular prevalence of Brucella species in smallholder dairy cattle in six regions of Tanzania from July 2019 to October 2020. Dairy cattle (n = 2048) were sampled from 1371 farms. DNA extracted from blood and vaginal swabs was tested for Brucella using qPCR targeting the IS711 gene and positives were tested for the alkB marker for B. abortus and BMEI1172 marker for B. melitensis. The molecular prevalence was 3.5% (95% CI: 2.8–4.4) with the highest prevalence 8.1% (95% CI: 4.6–13.0) in Njombe region. B. melitensis was the predominant species detected (66.2%). Further studies are recommended to understand the source of B. melitensis and its implications for veterinary public health. Livestock keepers should be informed of the risks and biosecurity practices to reduce the introduction and control of Brucella. Cattle and small ruminant vaccination programs could be implemented to control brucellosis in high-risk populations in the country.
Diagnostic challenges of brucellosis in humans and livestock in Tanzania: A thematic review
(CABI One Health, 2023-01-13) Mengele, Isaac; Shirima, Gabriel; Bronsvoort, Barend; Hernandez-Castro, Luis; Cook, Elizabeth
Brucellosis is an endemic bacterial zoonosis in Tanzania, and is among the most prioritized zoonotic diseases in the country. Brucellosis affects public health and livestock production in developing countries. Most human and livestock cases are not detected by the existing surveillance systems resulting in significant underestimation of the disease burden, and poor management of human cases by using nonspecific antibiotics may potentially contribute to antimicrobial resistance. To quantify the factors related to underreporting and those associated with the challenges in the diagnosis of brucellosis in Tanzania, search terms including “Brucella” “diagnosis” and “challenges” were used to query in Google search engine and publisher databases such as MEDLINE, PUBMED, NCBI, Springer, Hindawi, and Elsevier. The search parameters were limited to publications between 1995 and 2020. The searches returned 319 publications and grey articles which were screened and 57 were eligible for inclusion in this study. Four main areas were identified that cause underreporting of brucellosis and hinder brucellosis diagnosis: (1) inadequate knowledge of brucellosis among stakeholders in the livestock value chain, (2) limited diagnostic capacity for brucellosis due to unawareness of diagnostic tests and lack of epidemiological background of brucellosis among human and livestock health service workers (3) challenges associated with diagnostic tests, which include unreliable availability of diagnostic tests and unskilled workers, and (4) the uneven distribution of brucellosis surveillance studies in the country. This study suggests that there is a need for (1) training on public health education and brucellosis awareness among stakeholders in the livestock value chain; (2) providing scheduled continuing professional education with regard to brucellosis and other zoonotic diseases to health and livestock workers; (3) future brucellosis surveillance studies must focus on unrepresented regions; and (4) lastly, we recommend that the rose Bengal plate test (RBPT) and competitive enzyme-linked immunosorbent assay (cELISA) should be considered in brucellosis diagnostic schemes as a complementary tool to hasten the implementation of an ongoing national strategy for the prevention and control of brucellosis in humans and livestock in Tanzania. We suggest that these recommendations be considered for inclusion in the national strategy for brucellosis control in Tanzania. One Health Impact Statement Brucellosis is a disease caused by bacteria of genus Brucella and is transmitted from animals to humans. Humans get infected through ingestion of infected animal products but also through contact with bacteria via broken skin or inhalation of aerosolized bacteria particles during culture in the laboratory. Humans working with animals or animal products and laboratory personnel are at higher risk of infection. Tanzania has recently established a One-Health desk in the Prime Minister’s Office to address all matters related to One Health. However, the desk is in the infancy stage, more studies must be done to fill knowledge gaps so that working instruments became realistic. This review provides a synthesis of information that could be used by the One Health desk and other One Health stakeholders in the country on how to improve the existing brucellosis surveillance structures for improvement of One-Health service delivery in the country.
Epidemiology of leptospirosis in Tanzania: A review of the current status, serogroup diversity and reservoirs
(PLOS, 2021-11-16) Motto, Shabani; Shirima, Gabriel; Bronsvoort, Barend; Cook, Elizabeth
Background Tanzania is among the tropical countries of Sub-Saharan Africa with the environmental conditions favorable for transmission of Leptospira. Leptospirosis is a neglected zoonotic disease, and although there are several published reports from Tanzania, the epidemiology, genetic diversity of Leptospira and its host range are poorly understood. Methods We conducted a comprehensive review of human and animal leptospirosis within the 26 regions of the Tanzanian mainland. Literature searches for the review were conducted in PubMed and Google Scholar. We further manually identified studies from reference lists among retrieved studies from the preliminary search. Results We identified thirty-four studies describing leptospirosis in humans (n = 16), animals (n = 14) and in both (n = 4). The number of studies varied significantly across regions. Most of the studies were conducted in Morogoro (n = 16) followed by Kilimanjaro (n = 9) and Tanga (n = 5). There were a range of study designs with cross-sectional prevalence studies (n = 18), studies on leptospirosis in febrile patients (n = 13), a case control study in cattle (n = 1) and studies identifying novel serovars (n = 2). The most utilized diagnostic tool was the microscopic agglutination test (MAT) which detected antibodies to 17 Leptospira serogroups in humans and animals. The Leptospira serogroups with the most diverse hosts were Icterohaemorrhagiae (n = 11), Grippotyphosa (n = 10), Sejroe (n = 10), Pomona (n = 9) and Ballum (n = 8). The reported prevalence of Leptospira antibodies in humans ranged from 0.3–29.9% and risk factors were associated with occupational animal contact. Many potential reservoir hosts were identified with the most common being rodents and cattle. Conclusion Leptospirosis is prevalent in humans and animals in Tanzania, although there is regional and host variation in the reports. Many regions do not have information about the disease in either humans or their animal reservoirs. More studies are required to understand human leptospirosis determinants and the role of livestock in leptospirosis transmission to humans for the development of appropriate control strategies.
Epidemiology of Q-fever in domestic ruminants and humans in Africa. A systematic review
(CABI One Health, 2022-11-17) Bwatota, Shedrack; Cook, Elizabeth; Bronsvoort, Barend; Wheelhouse, Nick; Hernandez-Castro, Luis; Shirima, Gabriel
Q-fever is a zoonotic infectious disease caused by the gram-negative, intracellular, spore-forming bacterium Coxiella burnetii . Infected ruminants (cattle, sheep, and goats) are the reservoirs of the pathogen and thus an important source of infection in humans. This systematic review aims to consolidate the knowledge and awareness of Q-fever in Africa and identify future research opportunities and possible interventions in low-resource settings. We review information on Q-fever epidemiology and the diagnostic challenges in humans and domestic ruminants in Africa from the last 23 years. Six databases including university repositories were searched for relevant articles. A total of 84 studies and 4 theses met the selection criteria and were thus included in the review. They include serological and molecular studies of Q-fever in humans or domestic ruminants in 24/54 African countries. The mean seroprevalence estimates were 16% (95%CI 11–23%) in humans; 14% (95%CI 10–20%) in cattle; 13% (95%CI 9–18%) in sheep; and 21% (95%CI 15–29%) in goats. The mean prevalence for molecular detection of the pathogen were 3% (95%CI 0–16%) in humans; 9% (95%CI 4–19%) in cattle; 16% (95%CI 5–41%) in sheep; and 23% (95%CI 20–80%) in goats. The number of studies that identified risk factors for exposure among domestic ruminants was: sex (n = 6), age (n = 17), contact with other animals (n = 5), lack of quarantine of newly purchased animals (n = 1), extensive grazing system (n = 4), herd size (2), history of abortion (n = 5), absence of vaccination (n = 2), and high temperature (n = 1). The number of studies that reported protective factors was: sanitation (n = 2), burying and/ or burning the aborted foetus (n = 2), and young (age) (n = 2). The studies that identified risk factors for human disease infection included: close contact to animals (n = 7), age (n = 3), and gender (n = 5), while those identifying protective factors included: living in non-irrigated areas (n = 1), awareness/knowledge about zoonosis (n = 1), rodent control (n = 1), sanitation/disinfection of equipment after and before use (n = 1), occasional grazing (n = 1), and do nothing to aborted materials (n = 1). Diagnostic challenges such as poverty, lack of a well-equipped laboratory with biosafety level 3 specific for Q-fever testing, unspecific and self-limiting clinical signs/symptoms, lack of gold standard test, and variation in test specificity and sensitivity were identified. The disease is likely to be widespread in Africa and of public importance and underreported thus ‘One Health’ approaches to future studies are recommended. Further studies should focus on concurrent studies of human and livestock populations.
Genetic estimates and genome-wide association studies of antibody response in Tanzanian dairy cattle
(Frontiers Media SA, 2025-04-24) Hernandez-Castro, Luis; Cook, Elizabeth; Matika, Oswald; Mengele, Isaac; Motto, Shabani; Bwatota, Shedrack; Zirra-Shallangwa, Bibiana; Pong-Wong, Ricardo; Prendergast, James; Mrode, Raphael; Toye, Philip; Komwihangilo, Daniel; Lyatuu, Eliamoni; Karani, Benedict; Nangekhe, Getrude; Mwai, Ally; Shirima, Gabriel; Bronsvoort, Barend
Identifying the genetic determinants of host defence against infectious pathogens is central to enhancing disease resilience and therapeutic efficacy in livestock. Here, we investigated immune response heritability to important infectious diseases affecting smallholder dairy cattle using variance component analysis. We also conducted genome-wide association studies (GWAS) to identify genetic variants that may help understand the underlying biology of these health traits. By assessing 668,911 single-nucleotide polymorphisms (SNPs) genotyped in 2,045 crossbred cattle sampled from six regions of Tanzania, we identified high levels of interregional admixture and European introgression, which may increase infectious disease susceptibility relative to indigenous breeds. Heritability estimates were low to moderate, ranging from 0.03 (SE ± 0.06) to 0.44 (SE ± 0.07), depending on the health trait. GWAS results revealed several loci associated with seropositivity to the viral diseases Rift Valley fever and bovine viral diarrhoea, the protozoan parasites Neospora caninum and Toxoplasma gondii, and the bacterial pathogens Brucella sp, Leptospira hardjo, and Coxiella burnetii. The identified quantitative trait loci mapped to genes involved in immune defence, tumour suppression, neurological processes, and cell exocytosis. We propose that our results provide a basis for future understanding of the cellular pathways contributing to general and taxon-specific infection responses, and for advancing selective breeding and therapeutic target design.
Molecular epidemiology of Brucella species in mixed livestock-human ecosystems in Kenya
(Springer Nature Limited, 2021-04-23) Akoko, James; Pelle, Roger; Lukambagire, AbdulHamid; Machuka, Eunice; Nthiwa, Daniel; Mathew, Coletha; Fèvre, Eric; Bett, Bernard; Cook, Elizabeth; Othero, Doreen; Bonfoh, Bassirou; Kazwala, Rudovick; Shirima, Gabriel; Schelling, Esther; Halliday, Jo; Ouma, Collins
Brucellosis, caused by several species of the genus Brucella, is a zoonotic disease that affects humans and animal species worldwide. Information on the Brucella species circulating in different hosts in Kenya is largely unknown, thus limiting the adoption of targeted control strategies. This study was conducted in multi-host livestock populations in Kenya to detect the circulating Brucella species and assess evidence of host–pathogen associations. Serum samples were collected from 228 cattle, 162 goats, 158 sheep, 49 camels, and 257 humans from Narok and Marsabit counties in Kenya. Information on age, location and history of abortion or retained placenta were obtained for sampled livestock. Data on age, gender and location of residence were also collected for human participants. All samples were tested using genus level real-time PCR assays with primers specific for IS711 and bcsp31 targets for the detection of Brucella. All genus positive samples (positive for both targets) were further tested with a speciation assay for AlkB and BMEI1162 targets, specific for B. abortus and B. melitensis, respectively. Samples with adequate quantities aggregating to 577 were also tested with the Rose Bengal Test (RBT). A total of 199 (33.3%) livestock and 99 (38.5%) human samples tested positive for genus Brucella. Animal Brucella PCR positive status was positively predicted by RBT positive results (OR = 8.3, 95% CI 4.0–17.1). Humans aged 21–40 years had higher odds (OR = 2.8, 95% CI 1.2–6.6) of being Brucella PCR positive compared to the other age categories. The data on detection of different Brucella species indicates that B. abortus was detected more often in cattle (OR = 2.3, 95% CI 1.1–4.6) and camels (OR = 2.9, 95% CI 1.3–6.3), while B. melitensis was detected more in sheep (OR = 3.6, 95% CI 2.0–6.7) and goats (OR = 1.7, 95% CI 1.0–3.1). Both B. abortus and B. melitensis DNA were detected in humans and in multiple livestock host species, suggesting cross-transmission of these species among the different hosts. The detection of these two zoonotic Brucella species in humans further underpins the importance of One Health prevention strategies that target multiple host species, especially in the multi-host livestock populations.
Seroepidemiology of Leptospira serovar Hardjo and associated risk factors in smallholder dairy cattle in Tanzania
(PLOS ONE, 2023-04-05) Motto, Shabani; Hernandez-Castro, Luis; Shirima, Gabriel; Mengele, Isaac; Bwatota, Shedrack; Bronsvoort, Barend; Lyatuu, Eliamoni; Komwihangilo, Daniel; Cook, Elizabeth
Background Smallholder dairy farming is crucial for the Tanzanian dairy sector which generates income and employment for thousands of families. This is more evident in the northern and southern highland zones where dairy cattle and milk production are core economic activities. Here we estimated the seroprevalence of Leptospira serovar Hardjo and quantified potential risk factors associated with its exposure in smallholder dairy cattle in Tanzania. Methods From July 2019 to October 2020, a cross-sectional survey was carried out in a subset of 2071 smallholder dairy cattle. Information about animal husbandry and health management was collected from farmers, and blood was taken from this subset of cattle. Seroprevalence was estimated and mapped to visualize potential spatial hotspots. The association between a set of animal husbandry, health management and climate variables and ELISA binary results was explored using a mixed effects logistic regression model. Results An overall seroprevalence of 13.0% (95% CI 11.6–14.5%) for Leptospira serovar Hardjo was found in the study animals. There was marked regional variations with the highest seroprevalence in Iringa 30.2% (95% CI 25.1–35.7%) and Tanga 18.9% (95% CI 15.7–22.6) with odds ratios of OR = 8.13 (95% CI 4.23–15.63) and OR = 4.39 (95% CI 2.31–8.37), respectively. Multivariate analysis revealed the individual animal factors that were a significant risk for Leptospira seropositivity in smallholder dairy cattle were: animals over 5 years of age (OR = 1.41, 95% CI 1.05–1.9); and indigenous breed (OR = 2.78, 95% CI 1.47–5.26) compared to crossbred animals SHZ-X-Friesian (OR = 1.48, 95% CI 0.99–2.21) and SHZ-X-Jersey (OR = 0.85, 95% CI 0.43–1.63). Farm management factors significantly associated with Leptospira seropositivity included: hiring or keeping a bull for raising purposes (OR = 1.91, 95% CI 1.34–2.71); distance between farms of more than 100 meters (OR = 1.75, 95% CI 1.16–2.64); cattle kept extensively (OR = 2.31, 95% CI 1.36–3.91); farms without cat for rodent control (OR = 1.87, 95% CI 1.16–3.02); farmers with livestock training (OR = 1.62, 95% CI 1.15–2.27). Temperature (OR = 1.63, 95% CI 1.18–2.26), and the interaction of higher temperature and precipitation (OR = 1.5, 95%CI 1.12–2.01) were also significant risk factors. Conclusion This study indicated seroprevalence of Leptospira serovar Hardjo, as well as the risk factors driving dairy cattle leptospirosis exposure in Tanzania. The study showed an overall high leptospirosis seroprevalence with regional variations, where Iringa and Tanga represented the highest seroprevalence and risk. The study highlighted the urgent need to understand the human exposures and risks from this important zoonosis to develop control measures and awareness of the problem and quantify the economic and production impacts through abortion and milk loss. In addition, given that the available data was limited to Leptospira serovar Hardjo, the study recommends more studies to identify serologically the most common serovars in cattle for targeted vaccination and risk reduction.
Seroprevalence and Risk Factors for Q fever (Coxiella burnetii) Exposure in Smallholder Dairy Cattle in Tanzania
(MDPI, 2022-11-28) Bwatota, Shedrack; Shirima, Gabriel; Hernandez-Castro, Luis; Bronsvoort, Barend; Wheelhouse, Nick; Mengele, Isaac; Motto, Shabani; Komwihangilo, Daniel; Lyatuu, Eliamoni; Cook, Elizabeth
Q fever is a zoonotic disease, resulting from infection with Coxiella burnetii. Infection in cattle can cause abortion and infertility, however, there is little epidemiological information regarding the disease in dairy cattle in Tanzania. Between July 2019 and October 2020, a serosurvey was conducted in six high dairy producing regions of Tanzania. Cattle sera were tested for antibodies to C. burnetii using an indirect enzyme-linked immunosorbent assay. A mixed effect logistic regression model identified risk factors associated with C. burnetii seropositivity. A total of 79 out of 2049 dairy cattle tested positive with an overall seroprevalence of 3.9% (95% CI 3.06–4.78) across the six regions with the highest seroprevalence in Tanga region (8.21%, 95% CI 6.0–10.89). Risk factors associated with seropositivity included: extensive feeding management (OR 2.77, 95% CI 1.25–3.77), and low precipitation below 1000 mm (OR 2.76, 95% 1.37–7.21). The disease seroprevalence is relatively low in the high dairy cattle producing regions of Tanzania. Due to the zoonotic potential of the disease, future efforts should employ a “One Health” approach to understand the epidemiology, and for interdisciplinary control to reduce the impacts on animal and human health.
The Status and Risk Factors of Brucellosis in Smallholder Dairy Cattle in Selected Regions of Tanzania
(MDPI, 2023-02-14) Mengele, Isaac; Shirima, Gabriel; Bwatota, Shedrack; Motto, Shabani; Bronsvoort, Barend; Komwihangilo, Daniel; Lyatuu, Eliamoni; Cook, Elizabeth; Hernandez-Castro, Luis
Bovine brucellosis is a bacterial zoonoses caused by Brucella abortus. We conducted a cross-sectional study to determine brucellosis seroprevalence and risk factors among smallholder dairy cattle across six regions in Tanzania. We sampled 2048 dairy cattle on 1374 farms between July 2019 and October 2020. Sera were tested for the presence of anti-Brucella antibodies using a competitive enzyme-linked immunosorbent assay. Seroprevalence was calculated at different administrative scales, and spatial tests were used to detect disease hotspots. A generalized mixed-effects regression model was built to explore the relationships among Brucella serostatus, animals, and farm management factors. Seroprevalence was 2.39% (49/2048 cattle, 95% CI 1.7–3.1) across the study area and the Njombe Region represented the highest percentage with 15.5% (95% CI 11.0–22.0). Moreover, hotspots were detected in the Njombe and Kilimanjaro Regions. Mixed-effects models showed that having goats (OR 3.02, 95% C 1.22–7.46) and abortion history (OR 4.91, 95% CI 1.43–16.9) were significant risk factors for brucellosis. Education of dairy farmers regarding the clinical signs, transmission routes, and control measures for brucellosis is advised. A One Health approach is required to study the role of small ruminants in cattle brucellosis and the status of brucellosis in dairy farmers in the Njombe and Kilimanjaro Regions.