Bovine trypanosomiasis risk in an endemic area on the eastern plateau of Zambia

Breeding of African sheep reared under low-input/output smallholder production systems for trypanotolerance

Trypanosomiasis is a disease caused by unicellular protozoan parasites. Small ruminants succumb to trypanosomiasis in areas of high tsetse fly challenge, resulting in serious economic loss often to farmers in low-input smallholder systems. At present, trypanosomiasis is treated with trypanocidal drugs, but access to these can be limited, and increasing parasite resistance raises questions about their efficacy. The development of trypanotolerance in small ruminant flocks through targeted breeding strategies is considered a sustainable and economical option for controlling African trypanosomiasis. Recently, quantitative trait loci (QTLs) associated with trypanotolerance traits in sheep have been reported. The results of these studies form the basis for more studies to identify QTLs associated with trypanosomiasis resistance, particularly in African livestock species. For example, signatures of positive selection for trypanotolerance have been identified using genome-wide single-nucleotide polymorphism data. However, there are several challenges in performing genetic analyses using data from low-input smallholder systems, including a lack of recorded pedigree and production records and the need for large sample sizes when flock sizes are often fewer than 50 animals. Breeding strategies to improve trypanotolerance should also preserve existing genetic diversity as well as minimize excessive genetic introgression by trypanosusceptible breeds. This review discusses the possibilities of breeding for trypanosome tolerance/resistance in low-input/low-output small ruminant production systems. Potential challenges are outlined, and potential available genetic resources are described as a foundation for future work.

Policy and Linkages in the Application of a One Health System for Reporting and Controlling African Trypanosomiasis and Other Zoonotic Diseases in Zambia

The capacity to detect, control and manage emerging and re-emerging zoonotic diseases in Africa has been limited by a lack of utilisation of available reporting structures and policies to support programmes at national and local levels. This study explored the impact of the Zambian government policies on animal and human disease reporting and management and on One Health opportunities. An in-depth review and analysis of strengths, weaknesses, opportunities, and threats in the existing policies and reporting structures in the departments responsible for Veterinary Services, Health, and Wildlife, was conducted. According to our findings, sub-optimal implementation of existing policies related to the control of zoonotic diseases was impacting disease reporting, and reporting structures play an important role in effective and sustainable reporting of zoonotic diseases. Further, the study explored capacities and strategies in trypanosomiasis control as a case study that could prompt effective adoption of a One Health approach, and as such, the study suggests measures that could help to assess the performance of a One Health system in the control of African trypanosomiasis and other zoonotic diseases.

Occurrence, diversity and distribution of Trypanosoma infections in cattle around the Akagera National Park, Rwanda

BACKGROUND

African Trypanosomiases threaten the life of both humans and animals. Trypanosomes are transmitted by tsetse and other biting flies. In Rwanda, the African Animal Trypanosomiasis (AAT) endemic area is mainly around the tsetse-infested Akagera National Park (NP). The study aimed to identify Trypanosoma species circulating in cattle, their genetic diversity and distribution around the Akagera NP.

METHODOLOGY

A cross-sectional study was carried out in four districts, where 1,037 cattle blood samples were collected. The presence of trypanosomes was determined by microscopy, immunological rapid test VerY Diag and PCR coupled with High-Resolution Melt (HRM) analysis. A parametric test (ANOVA) was used to compare the mean Packed cell Volume (PCV) and trypanosomes occurrence. The Cohen Kappa test was used to compare the level of agreement between the diagnostic methods.

FINDINGS

The overall prevalence of trypanosome infections was 5.6%, 7.1% and 18.7% by thin smear, Buffy coat technique and PCR/HRM respectively. Microscopy showed a low sensitivity while a low specificity was shown by the rapid test (VerY Diag). Trypanosoma (T.) congolense was found at a prevalence of 10.7%, T. vivax 5.2%, T. brucei brucei 2% and T. evansi 0.7% by PCR/HRM. This is the first report of T.evansi in cattle in Rwanda. The non-pathogenic T. theileri was also detected. Lower trypanosome infections were observed in Ankole x Friesian breeds than indigenous Ankole. No human-infective T. brucei rhodesiense was detected. There was no significant difference between the mean PCV of infected and non-infected animals (p>0.162).

CONCLUSIONS

Our study sheds light on the species of animal infective trypanosomes around the Akagera NP, including both pathogenic and non-pathogenic trypanosomes. The PCV estimation is not always an indication of trypanosome infection and the mechanical transmission should not be overlooked. The study confirms that the area around the Akagera NP is affected by AAT, and should, therefore, be targeted by the control activities. AAT impact assessment on cattle production and information on the use of trypanocides are needed to help policymakers prioritise target areas and optimize intervention strategies. Ultimately, these studies will allow Rwanda to advance in the Progressive Control Pathway (PCP) to reduce or eliminate the burden of AAT.

Epidemiological investigation of bovine trypanosomosis in Bedele district, Buno Bedele zone, Oromia regional state, Ethiopia

A cross-sectional study was conducted in December 2018 in four purposively selected villages of Bedele district, Oromia Regional State, Southwest Ethiopia. The study aimed to determine the prevalence of bovine trypanosomosis and associated risk factors of trypanosome infections in cattle. A total of 384 blood samples were collected from systematically selected cattle and examined using buffy coat and thin blood smear examination methods. The overall prevalence of bovine trypanosomosis was 8.3%. Trypanosoma congolense (68.8%) and T. vivax (31.2%) were the prevailing trypanosome species identified in the area. A statistically significant difference (P < 0.05) was observed in the prevalence of bovine trypanosomosis between body condition scores of cattle. The prevalence of bovine trypanosomosis was slightly higher in female (9%) as opposed to male (7.3%) cattle, but the difference was not statistically significant (P > 0.05). Similarly, no statistically significant difference (P > 0.05) was observed between age categories of cattle. The mean PCV value of trypanosome infected cattle (21.4 ± 3.6) was significantly (P < 0.05) lower than that of non-infected (25.6 ± 4.6). The current study indicated that, despite vector control measures implemented for several years, bovine trypanosomosis persists and continues to be a core problem to cattle health and production in the Bedele district. Therefore, more attention should be given to control the disease and its vectors based on temporal and spatial distribution. Also, the use of molecular techniques should be encouraged in view of their greater sensitivity when compared to the buffy coat method.

Challenges in the Diagnostic Performance of Parasitological and Molecular Tests in the Surveillance of African Trypanosomiasis in Eastern Zambia

African animal trypanosomiasis (AAT) control programs rely on active case detection through the screening of animals reared in disease endemic areas. This study compared the application of the polymerase chain reaction (PCR) and microscopy in the detection of trypanosomes in cattle blood in Mambwe, a rural district in eastern Zambia. Blood samples were collected from 227 cattle and tested for infection with trypanosomes using microscopy and Ribosomal RNA Internal Transcribed Spacers (ITS)-PCR. Microscopy on the buffy coat detected 17 cases, whilst thin and thick smears detected 26 cases and 28 cases, respectively. In total, microscopy detected 40 cases. ITS-PCR-filter paper (FP) on blood spots stored on FP detected 47 cases, and ITS-PCR-FTA on blood spots stored on Whatman FTA Classic cards detected 83 cases. Using microscopy as the gold standard, ITS-PCR-FTA had a better specificity (SP) and sensitivity (SE) (SP = 72.2%; SE = 77.5%; kappa = 0.35) than ITS-PCR-FP (SP = 88%; SE = 60%; kappa = 0.45). The prevalence of Trypanosoma brucei s.l. was higher on ITS-PCR-FTA (19/227) than on ITS-PCR-FP (0/227). Our results illustrate the complexities around trypanosomiasis surveillance in rural Africa and provide evidence of the impact that field conditions and staff training can have on diagnostic results, which in turn impact the success of tsetse and trypanosomiasis control programs in the region.

Prioritizing smallholder animal health needs in East Africa, West Africa, and South Asia using three approaches: Literature review, expert workshops, and practitioner surveys

Managing the health needs of livestock contributes to reducing poverty and improving the livelihoods of smallholder and pastoralist livestock keepers globally. Animal health practitioners, producers, policymakers, and researchers all must prioritize how to mobilize limited resources. This study employed three approaches to prioritize animal health needs in East and West Africa and South Asia to identify diseases and syndromes that impact livestock keepers. The approaches were a) systematic literature review, b) a series of expert workshops, and c) a practitioner survey of veterinarians and para-veterinary professionals. The top constraints that emerged from all three approaches include endo/ ectoparasites, foot and mouth disease, brucellosis, peste des petits ruminants, Newcastle disease, and avian influenza. Expert workshops additionally identified contagious caprine pleuropneumonia, contagious bovine pleuropneumonia, mastitis, and reproductive disorders as constraints not emphasized in the literature review. Practitioner survey results additionally identified nutrition as a constraint for smallholder dairy and pastoralist small ruminant production. Experts attending the workshops agreed most constraints can be managed using existing veterinary technologies and best husbandry practices, which supports a shift away from focusing on individual diseases and new technologies towards addressing systemic challenges that limit access to veterinary services and inputs. Few research studies focused on incidence/ prevalence of disease and impact, suggesting better incorporation of socio-economic impact measures in future research would better represent the interests of livestock keepers.

Bovine trypanosomosis: Prevalence and vector distribution in Sadi Chanka district, Kellem Wollega zone, Oromia regional state, Ethiopia

Bovine trypanosomosis remains an important livestock disease constraint, which is threatening livestock health and production, despite ongoing tsetse and trypanosomosis control efforts in Sadi Chanka district, Kellem Wollega zone, Oromia regional state, Ethiopia. A cross-sectional study was conducted in May 2018, to determine the prevalence of bovine trypanosomosis and distribution of the vectors of disease in Sadi Chanka district, Western Ethiopia. A total of 370 blood samples were collected from randomly selected local Horro and Abigar cattle breeds covering five villages of the district. The collected samples were examined using buffy coat microscopy and Giemsa-stained thin blood smear techniques. In this study, 12.4% (95% CI: 12.3-12.4) of the animals were found to be infected with trypanosomes. The study showed that 69.6% of trypanosome infections were caused by T. congolense followed by 26.1% T. vivax and 4.3% mixed T. congolense and T. vivax. In the present study, the association of bovine trypanosomosis was assessed in releation to body condition scores, sex, and age of cattle, and a significant association (P < 0.05) was observed between body condition scores. However, significant differences were not observed between sex and age categories (P > 0.05). The Mean Packed Cell Volume (PCV) of infected (21.6%) and non-infected (24.5%) groups of cattle had significant variation (P < 0.05). In an entomological survey, a total of 616 flies were trapped, of which 280 (45.5%) were Glossina and the remaining 336 (54.5%) were Stomoxys, Tabanus, and Haematopota. The apparent density of Glossina, Stomoxys, Tabanus, and Haematopota was 3.5, 3.1, 0.7 and 0.4 fly per trap per day, respectively. This study generated basic scientific data on the epidemiology of bovine trypanosomosis and its vectors in Sadi Chanka district, which can be used in planning the control of bovine trypanosomosis in the area.

A one health investigation of pathogenic trypanosomes of cattle in Malawi

Parasitic protozoan trypanosomes of the genus Trypanosoma cause infections in both man and livestock in Africa. Understanding the current spatial distribution of trypanosomes, herd-level factors associated with Trypanosoma brucei infection as well as local knowledge of African trypanosomosis is key to its prevention and control. A cross-sectional study was performed that sampled 53 livestock farmers and 444 cattle throughout Malawi. Cattle were screened for trypanosomes using serology and molecular techniques. Questionnaires were administered to livestock herders and incidence of hospital diagnosed human trypanosome infections was estimated from reports submitted to the Department of Health Unit. The apparent prevalence of trypanosome species based on molecular detection was low for Trypanosoma brucei (2%; 95 % CI: 1-4 %) and Trypanosoma congolense (3%; 95 % CI: 2-5 %) but higher for Trypanosoma theileri (26 %; 95 % CI: 22-30 %). The central region of the country was identified as being at a higher risk of T.brucei infection. One of the sampled cattle was confirmed as being infected with Trypanosoma brucei rhodesiense. Human trypanosome cases were more frequently reported in the northern region with an estimated incidence of 5.9 cases per 100,000 people in Rumphi District. The control of zoonotic diseases that impact poor livestock herders requires a One Health approach due to the close contact between humans and their animals and the reliance on animal production for a sustainable livelihood.

Insights into the Control and Management of Human and Bovine African Trypanosomiasis in Zambia between 2009 and 2019-A Review

Tsetse transmitted trypanosomiasis is a fatal disease commonly known as Nagana in cattle and sleeping sickness in humans. The disease threatens food security and has severe economic impact in Africa including most parts of Zambia. The level of effectiveness of commonly used African trypanosomiasis control methods has been reported in several studies. However, there have been no review studies on African trypanosomiasis control and management conducted in the context of One Health. This paper therefore seeks to fill this knowledge gap. A review of studies that have been conducted on African trypanosomiasis in Zambia between 2009 and 2019, with a focus on the control and management of trypanosomiasis was conducted. A total of 2238 articles were screened, with application of the search engines PubMed, PubMed Central and One Search. Out of these articles, 18 matched the required criteria and constituted the basis for the paper. An in-depth analysis of the 18 articles was conducted to identify knowledge gaps and evidence for best practices. Findings from this review provide stakeholders and health workers with a basis for prioritisation of African trypanosomiasis as an important neglected disease in Zambia and for formulation of One Health strategies for better control and/or management of the disease.

Diversity of trypanosomes in wildlife of the Kafue ecosystem, Zambia

The Kafue ecosystem is a vast conservation protected area comprising the Kafue National Park (KNP) and the Game Management Areas (GMA) that act as a buffer around the national park. The KNP has been neglected as a potential foci for rhodesiense sleeping sickness despite the widespread presence of the tsetse vector and abundant wildlife reservoirs. The aim of this study was to generate information on circulating trypanosomes and their eminent threat/risk to public health and livestock production of a steadily growing human and livestock population surrounding the park. We detected various trypanosomes circulating in different mammalian wildlife species in KNP in Zambia by applying a high throughput ITS1-polymerase chain reaction (PCR)/nanopore sequencing method in combination with serum resistant associated-PCR/Sanger sequencing method. The prevalence rates of trypanosomes in hartebeest, sable antelope, buffalo, warthog, impala and lechwe were 6.4%, 37.2%, 13.2%, 11.8%, 2.8% and 11.1%, respectively. A total of six trypanosomes species or subspecies were detected in the wildlife examined, including Trypanosoma brucei brucei, T. godfreyi, T. congolense, T. simiae and T. theileri. Importantly we detected human infective T. b. rhodesiense in buffalo and sable antelope with a prevalence of 9.4% and 12.5%, respectively. In addition, T. b. rhodesiense was found in the only vervet monkey analyzed. The study thus reaffirmed that the Kafue ecosystem is a genuine neglected and re-emerging foci for human African trypanosomiasis. This is the first assessment of the trypanosome diversity circulating in free-ranging wildlife of the KNP.

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Detected six African trypanosomes in wildlife species of Kafue National Park using ITS1-PCR and Nanopore sequencing method.

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Confirmed presence of Trypanosoma brucei rhodesiense using SRA PCR.

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Identified unique divergence of SRA sequence of Trypanosoma brucei rhodesiense from buffalo, sable and vervet monkey.

Integrated cost-benefit analysis of tsetse control and herd productivity to inform control programs for animal African trypanosomiasis

Background

Animal African trypanosomiasis (AAT) and its tsetse vector are responsible for annual losses estimated in billions of US dollars ($). Recent years have seen the implementation of a series of multinational interventions. However, actors of AAT control face complex resource allocation decisions due to the geographical range of AAT, diversity of ecological and livestock systems, and range of control methods available.

Methods

The study presented here integrates an existing tsetse abundance model with a bio-economic herd model that captures local production characteristics as well as heterogeneities in AAT incidence and breed. These models were used to predict the impact of tsetse elimination on the net value of cattle production in the districts of Mambwe, in Zambia, and Faro et Déo in Cameroon. The net value of cattle production under the current situation was used as a baseline, and compared with alternative publicly funded control programmes. In Zambia, the current baseline is AAT control implemented privately by cattle owners (Scenario Z0). In Cameroon, the baseline (Scenario C0) is a small-scale publicly funded tsetse control programme and privately funded control at farm level. The model was run for 10 years, using a discount rate of 5%.

Results

Compared to Scenario C0, benefit-cost ratios (BCR) of 4.5 (4.4–4.7) for Scenario C1 (tsetse suppression using insecticide treatment of cattle (ITC) and traps + maintenance with ITC barrier), and 3.8 (3.6–4.0) for Scenario C2 (tsetse suppression using ITC and traps + maintenance with barrier of targets), were estimated in Cameroon. For Zambia, the benefit-cost ratio calculated for Scenarios Z1 (targets, ITC barrier), Z2 (targets, barrier traps), Z3 (aerial spraying, ITC barrier), and Z4 (aerial spraying, barrier traps) were 2.3 (1.8 - 2.7), 2.0 (1.6-2.4), 2.8 (2.3–3.3) and 2.5 (2.0–2.9), respectively. Sensitivity analysis showed that the profitability of the projects is relatively resistant to variations in the costs of the interventions and their technical efficiency.

Conclusions

It is envisioned that the methodologies presented here will be useful for the evaluation and design of existing and future control programmes, ensuring they have tangible benefits in the communities they are targeting.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2679-x) contains supplementary material, which is available to authorized users.

Bovine trypanosomosis: changes in parasitemia and packed cell volume in dry and wet seasons at Gidami District, Oromia Regional State, western Ethiopia

BACKGROUND

Animal trypanosomosis is one of the major disease problems affecting agricultural productivity in Ethiopia. The impact of the disease is believed to vary with season and agro-ecologies in line with fly vector distribution. A cross-sectional study on bovine trypanosomosis was conducted from November 2015 to June 2016, in seven selected villages of Gidami district, Oromia Regional State, western Ethiopia. A total of 930 blood samples were collected and subjected to parasitological and hematological analysis.

RESULT

The overall prevalence of bovine trypanosomosis was 14.1%. The seasonal prevalence shows 9.06% in early dry and 18.4% in early rainy seasons. Three trypanosome species, Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei were identified in the examined animals. T. congolense followed by T. vivax were the predominant species (respectively 59.0 and 35.9% in early dry season and 62.0 and 22.8% in early rainy season). The prevalence of T. vivax remained similar in both early dry and early rainy seasons in both lowland and midland agroecologies whereas T. congolense was more dominant in the lowland area in both seasons compared to mid land study sites. The disease was more prevalent in lowland (23.9%) compared to midland (11.1%) during early rainy season (P < 0.001) whereas no significant difference was observed between the two agroecologies during early dry season (P = 0.165). Packed cell volume (PCV) was much lower in parasitemic animals than in aparasitemic cattle whereas the mean PCV value for parasitemic animals (20.36%; 95% CI 19.56 to 21.16) in early dry season was similar to values in early rainy season (20.46%, 95% CI 18.84 to 21.08%). A similar situation was noticed for animals in both low land and mid land study sites.

CONCLUSION

Overall, the detection of trypanosomes in blood was significantly affected by agro-ecology, season and body condition of the animals. Special emphasis should be given to integrated trypanosomosis management in early rainy months where fly population is believed to start increasing.

Molecular survey of pathogenic trypanosomes in naturally infected Nigerian cattle

Microscopy and polymerase chain reaction (PCR) were used to survey pathogenic trypanosome infection in naturally infected Nigerian cattle. In 411 animals sampled, microscopy detected 15.1% positive infection of at least one of Trypanosoma brucei, Trypanosoma congolense or Trypanosoma vivax, while PCR detected 63.7% positive infections of at least one of those species and Trypanosoma evansi. PCR detected 4.4%, 48.7%, 26.0% and 0.5% respectively of T. brucei, T. congolense, T. vivax and T. evansi infections. All of the T. congolense detected were savannah-type, except for two forest-type infections. Prevalence of mixed infections was 13.9%, being primarily co-infection by T. congolense and T. vivax while prevalence of mixed infections by T. evansi, T. vivax and T. congolense was 1.5%. Microscopy showed poor sensitivity but specificity greater than 94%. Infection rates were much higher in Southern than in Northern Nigeria. Infections were lowest in N'dama compared to Muturu, Sokoto Gudali and White Fulani breeds. Animals with T. vivax monoinfection and mixed infections showed significantly lower packed cell volume (PCV) values. Those infected with any Trypanosoma species with <200 parasites/μl showed higher PCV values than those infected with >200 parasites/μl. The new finding of savannah- and forest-type T. congolense in Nigeria and the relatively high abundance of mixed infections are of significant clinical relevance. This study also suggests that T. congolense is the most prevalent species in Nigeria.