Prevalence and incidence of bovine trypanosomosis on the Adamaoua plateau in Cameroon 10 years after the tsetse eradication campaign

Prevalence of Spiroplasma and interaction with wild Glossina tachinoides microbiota

Tsetse flies (Diptera: Glossinidae) are vectors of the tropical neglected diseases sleeping sickness in humans and nagana in animals. The elimination of these diseases is linked to control of the vector. The sterile insect technique (SIT) is an environment-friendly method that has been shown to be effective when applied in an area-wide integrated pest management approach. However, as irradiated males conserve their vectorial competence, there is the potential risk of trypanosome transmission with their release in the field. Analyzing the interaction between the tsetse fly and its microbiota, and between different microbiota and the trypanosome, might provide important information to enhance the fly's resistance to trypanosome infection. This study on the prevalence of Spiroplasma in wild populations of seven tsetse species from East, West, Central and Southern Africa showed that Spiroplasma is present only in Glossina fuscipes fuscipes and Glossina tachinoides. In G. tachinoides, a significant deviation from independence in co-infection with Spiroplasma and Trypanosoma spp. was observed. Moreover, Spiroplasma infections seem to significantly reduce the density of the trypanosomes, suggesting that Spiroplasma might enhance tsetse fly's refractoriness to the trypanosome infections. This finding might be useful to reduce risks associated with the release of sterile males during SIT implementation in trypanosome endemic areas.

Zoo-Sanitary Situation Assessment, an Initial Step in Country Disease Prioritization Process: Systematic Review and Meta-Analysis from 2000 to 2020 in Cameroon

To prevent and/or control infectious diseases in animal and human health, an appropriate surveillance system based on suitable up-to-date epidemiological data is required. The systematic review protocol was designed according to the PRISMA statement to look at the available data on infectious diseases of livestock in Cameroon from 2000-2020. Data were searched through online databases. Grey literature was comprised of dissertations and theses from veterinary higher education institutions in Cameroon. A random-effects model was used to calculate pooled prevalence using Comprehensive Meta-Analysis Software. Based on disease prevalence, major infectious diseases of livestock in Cameroon were gastrointestinal parasitosis (57.4% in cattle, 67.2% in poultry, 88% in pigs), hemoparasites (21.6% in small ruminants, 19.7% in cattle), bovine pasteurellosis (55.5%), fowl salmonellosis (48.2%), small ruminant plague (39.7%), foot-and-mouth disease (34.5% in cattle), and African swine fever (18.9%). Furthermore, other important endemic zoonoses in the country included: Rift Valley fever (10.9% in cattle, 3.7% in small ruminants), brucellosis (7% in cattle, 8% in pigs), bovine tuberculosis (4.7% in cattle), hepatitis E virus (8.4% in pigs) and bovine leptospirosis (2.5%). Most of the retrieved research were carried out in the Adamawa, Northwest, and West regions of Cameroon. The evaluation of existing data as evidence, albeit publication-specific, is an important step towards the process of prioritizing animal diseases, including zoonoses.

Trypanosome infections in animals from tsetse infected areas of Cameroon and their sensitivity and resistance molecular profiles for diminazene aceturate and isometamidium chloride

Monitoring and assessment of control strategies for African trypanosomoses' elimination require not only updating data on trypanosome infections, but also to have an overview on the molecular profiles of trypanocides resistance in different epidemiological settings. This study was designed to determine, in animals from six tsetse-infested areas of Cameroon, the prevalence of trypanosome infections as well as the diminazene aceturate (DA) and isometamidium chloride (ISM) sensitivity/resistance molecular profiles of these trypanosomes. From 2016 to 2019, blood was collected in pigs, dogs, sheep, goats and cattle from six tsetse infested areas of Cameroon. DNA was extracted from blood and trypanosome species were identified by PCR. The sensitivity/resistance molecular profiles of trypanosomes to DA and ISM were investigated using PCR-RFLP. From 1343 blood samples collected, Trypanosoma vivax, Trypanosoma congolense forest and savannah, Trypanosoma theileri and trypanosomes of the sub-genus Trypanozoon were identified. The overall prevalence of trypanosome infections was 18.7%. These prevalence vary between trypanosome species, animal taxa, within and between sampling sites. Trypanosoma theileri was the predominant species with an infection rate of 12.1%. Trypanosomes showing resistant molecular profiles for ISM and DA were identified in animals from Tibati (2.7% for ISM and 65.6% for DA) and Kontcha (0.3% for ISM and 6.2% for DA). No trypanosome carrying resistant molecular profile for any of the two trypanocides was detected in animals from Fontem, Campo, Bipindi and Touboro. Mixed molecular profiles of sensitive/resistant trypanosomes were detected in animals from Tibati and Kontcha. Results of this study highlighted the presence of various trypanosome species as well as parasites carrying sensitive/resistant molecular profiles for DA and ISM in animals of tsetse infested areas of Cameroon. They indicate that the control strategies must be adapted according to epidemiological settings. The diversity of trypanosomes indicates that AAT remains a serious threat for animal breeding and animal health in these tsetse infested areas.

Diversity of tsetse flies and trypanosome species circulating in the highly infested cattle rearing area of the Faro and Deo subdivision, Adamawa region, Cameroon

Animal African Trypanosomiasis (AAT) remains an animal health problem in sub-Saharan Africa and in Cameroon in particular. Despite more than 40 years of fighting against AAT in some tsetse infested areas, the disease prevalence is still a concern. Improving the control strategies in different settings requires to understand the current epidemiological situation of AAT. The aim of the present study was to update our knowledge on the diversity of tsetse fauna and trypanosome species in the tsetse infested area of Faro and Deo division, Adamawa region, Cameroon. Tsetse flies were caught using Vavoua trap in two villages and the apparent density per trap (ADP) were estimated. After morphological identification of tsetse fly species, flies were dissected and their midguts recovered. The presence of blood meal residues was recorded. Trypanosomes species were checked in the flies' midguts by microscopy followed by PCR method. The vertebrate taxa on which tsetse flies have taken blood meal were determined using the heteroduplex-PCR method. A total of 338 tsetse flies including 11 teneral flies (10 Glossina palpalis palpalis and 01 G. morsitans submorsitans) and 327 non-teneral were trapped in Mayo Lainde and Tchabal Mbabo. Amongst the caught tsetse flies, of the 327 non-teneral flies, 315 (96.3%) were G. p. palpalis, 8 (2.4%) were G. morsitans submorsitans and 4 (1.2%) G. fuscipes fuscipes. Trypanosome infections including Trypanosoma congolense forest (19.88%) and savanah (2.53%) "types", T. brucei s.l. (7.30%) and T. vivax (2.85%) were identified in 45.08% of non-teneral flies (32.38% for single infection and 12.70% for mixed infection). Amongst the 54 blood meals identified in tsetse midguts, 41% were from humans, 33% from cattle and 26% from other vertebrate hosts. About 51.9% of blood meals were found with various trypanosome species including 42.6% with T. congolense and 24% with T. brucei s.l. This study revealed the presence of three tsetse taxa and the circulation of four trypanosome taxa in villages of the Faro and Deo division. About 45% of captured tsetse fly are infected with trypanosome species causing AAT. Tsetse flies feed on humans, cattle and many other vertebrates. Strategies to eliminate the vectors must be improved to reduce the pathological impacts of trypanosome infections in this area.

Environmental mutations in the Campo focus challenge elimination of sleeping sickness transmission in Cameroon

Sleeping sickness is still prevalent in Campo, southern Cameroon, despite the efforts of World Health Organization and the National Control Programme in screening and treating cases. Reducing disease incidence still further may need the control of tsetse vectors. We update entomological and parasitological parameters necessary to guide tsetse control in Campo. Tsetse flies were trapped, their apparent densities were evaluated as the number of flies captured per trap per day and mapped using GIS tools. Polymerase chain reaction based methods were used to identify their trypanosome infection rates. Glossina palpalis palpalis was the dominant vector species representing 93.42% and 92.85% of flies captured respectively during the heavy and light dry seasons. This species presented high densities, that is, 3.87, 95% CI [3.84-3.91], and 2.51, 95% CI [2.49-2.53] flies/trap/day in the two seasons. Moreover, 16.79% (of 1054) and 20.23% (of 1132 flies) were found infected with at least 1 trypanosome species for the 2 seasons respectively, Trypanosoma congolense being the most prevalent species, and Trypanosoma. brucei gambiense identified in 4 samples. Tsetse flies are abundant in Campo and present high trypanosome infection rates. The detection of tsetse infected with human trypanosomes near the newly created palm grove show workers' exposition. Tsetse densities maps built will guide vector control with 'Tiny Targets'.

African Animal Trypanosomiasis: A Systematic Review on Prevalence, Risk Factors and Drug Resistance in Sub-Saharan Africa

African animal trypanosomiasis (AAT) a parasitic disease of livestock in sub-Saharan Africa causing tremendous loses. Sub-Saharan continental estimation of mean prevalence in both large and small domestic animals, risk factors, tsetse and non-tsetse prevalence and drug resistance is lacking. A review and meta-analysis was done to better comprehend changes in AAT prevalence and drug resistance. Publish/Perish software was used to search and extract peer-reviewed articles in Google scholar, PubMed and CrossRef. In addition, ResearchGate and African Journals Online (AJOL) were used. Screening and selection of articles from 2000-2021 was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Articles 304 were retrieved; on domestic animals 192, tsetse and non-tsetse vectors 44, risk factors 49 and trypanocidal drug resistance 30. Prevalence varied by, host animals in different countries, diagnostic methods and species of Trypanosoma. Cattle had the highest prevalence with Ethiopia and Nigeria leading, T. congolense (11.80-13.40%) and T. vivax (10.50-18.80%) being detected most. This was followed by camels and pigs. Common diagnostic method used was buffy coat microscopy. However; polymerase chain reaction (PCR), CATT and ELISA had higher detection rates. G. pallidipes caused most infections in Eastern regions while G. palpalis followed by G. mortisans in Western Africa. Eastern Africa reported more non-tsetse biting flies with Stomoxys leading. Common risk factors were, body conditions, breed type, age, sex and seasons. Ethiopia and Nigeria had the highest trypanocidal resistance 30.00-35.00% and highest AAT prevalence. Isometamidium and diminazene showed more resistance with T. congolense being most resistant species 11.00-83.00%.

Spatial meta-analysis of the occurrence and distribution of tsetse-transmitted animal trypanosomiasis in Cameroon over the last 30 years

In Cameroon, >90% of cattle are considered exposed to African animal trypanosomiasis (AAT) infection, with the presence of tsetse rendering cattle husbandry as a very difficult proposition. A systematic review of data on AAT and tsetse from 1990 to 2021 was conducted to develop a national atlas. The review identified 74 relevant scientific documents, with three pathogenic Trypanosoma species (Trypanosoma vivax , T. congolense and T. brucei s.l.) most frequently identified as causing AAT. Trypanosoma grayi , T. theileri , T. simiae and the human African trypanosomiasis causative agent T. brucei gambiense were also identified in a wide range of hosts. The tsetse fly fauna of Cameroon comprises nine species, with Glossina palpalis palpalis and G. fuscipes fuscipes the most widely distributed following their identification in seven and five of the 10 regions, respectively. Two species, Glossina nigrofusca and G. pallicera pallicera appeared to be rare and were restricted to both forest and protected areas. The presence of AAT is associated with the presence of tsetse in the livestock–human–wildlife interface of Cameroon. AAT occurs beyond the tsetse belts of the country where mechanical vectors are abundant. This study provides AAT and tsetse maps to support ongoing interventions in Cameroon.

Molecular identification of different trypanosome species in tsetse flies caught in the wildlife reserve of Santchou in the western region of Cameroon

Addressing the problems linked to tsetse-transmitted trypanosomiases requires considerable data on tsetse distribution and trypanosome infections. Although efforts to map tsetse and trypanosome infections have been undertaken at continental level, published data are still rare in wildlife reserves of West and Central Africa. To fill this gap, data on tsetse distribution and trypanosome infections were generated in the wildlife reserve of Santchou. For this study, each tsetse caught was identified and its DNA extracted. Different trypanosome species were identified by PCR. Entomological and parasitological data were transported onto a satellite image in order to visualize their distributions. From 195 Glossina palpalis palpalis that were caught, 33.8% (66/195) carried trypanosome infections with 89.4% (59/66) of single infections and 10.6% (7/66) mixed infections. From the 66 flies with trypanosome infections, 54.5% (36/66), 27.3% (18/66) and 18.2% (12/66) were respectively due to Trypanosoma congolense, Trypanosoma brucei s.l. and Trypanosoma vivax. The global infection rates were 18.5% (36/195) for Trypanosoma congolense (forest and savannah), 9.2% (18/195) for Trypanosoma brucei s.l. and 6.1% (12/195) for Trypanosoma vivax. The maps generated show the distribution of tsetse and trypanosome infections. This study showed an active transmission of trypanosomes in the wildlife reserve of Santchou. The maps enabled to identify areas with high transmission risk and where control operations must be implemented in order to eliminate tsetse and the diseases that they transmit.

Molecular identification of diminazene aceturate resistant trypanosomes in tsetse flies from Yoko in the Centre region of Cameroon and its epidemiological implications

African animal trypanosomiases are caused by trypanosomes cyclically or mechanically transmitted by tsetse and other biting flies. Although molecular tools have been developed to identify drug-resistant trypanosomes in mammals, little or no investigation on drug-resistance has been undertaken on trypanosomes harbored by tsetse flies. Moreover, no data on mechanical vectors of African trypanosomes is available in most endemic areas of Cameroon. This study was designed to update our knowledge on the cyclical and mechanical vectors of African trypanosomes, and using molecular tools to identify different trypanosome species as well as diminazene aceturate resistant trypanosomes in tsetse flies trapped at Yoko in the Centre region of Cameroon.

For this study, traps were used to catch tsetse and mechanical vectors of African trypanosomes. The flies trapped were counted and identified by sex and species. DNA was extracted from tsetse and species-specific primers were used to identify different trypanosome species. PCR-RFLP was used to detect diminazene aceturate resistant strains of Trypanosoma congolense.

In all, 454 flies comprising 168 (37%) Tabanus spp., 71 (15.6%) Stomoxys spp. and 215 (47.4%) tsetse fly (i.e. 107 (49.8%) Glossina fusca congolensis, 71 (33%) Glossina fusca fusca and 37 (17.2%) Glossina palpalis palpalis) were trapped. Trypanosome infections were identified in 12.6% (27/215) of tsetse flies: 13 in G. f. congolensis, 6 in G. p. palpalis and 5 in G. f. fusca. From 24 T. congolense positive samples, PCR-RFLP was successful on 37.5% of the samples. Four samples (16.2%) harbored T. congolense strains that were resistant to diminazene aceturate while the remaining samples had drug-sensitive strains.

These results show for the first time the applicability of molecular tools for the identification of drug-resistant trypanosomes in tsetse. They revealed the existence of diminazene aceturate resistant strains of T. congolense in the tsetse-infested area of Yoko in the Centre region of Cameroon. Detection of drug-resistant trypanosomes in tsetse may enable scientists to map with accuracy specific areas where these parasites are transmitted. With such mapping, control strategies against African trypanosomiases could be improved by adapting control measures according to drug resistance distribution.

Widespread co-endemicity of Trypanosoma species infecting cattle in the Sudano-Sahelian and Guinea Savannah zones of Cameroon

Background

African animal trypanosomosis remains the major constraint of livestock production and livelihood of pastoral communities in Cameroon. Despite several decades of vector and parasite control efforts, it has not been eradicated. Alternative and sustainable control strategies require a sound knowledge of the local species, strains and vectors. In the Sudano-Sahelian and Guinea Savannah of Cameroon the prevalence and genetic diversity of trypanosomes infecting cattle was investigated by microscopy of cattle blood buffy coat and molecular methods using generic primers targeting parts of the internal transcribed spacer 1 (ITS-1) and encoded glycosomal glyceraldehyde 3-phosphate dehydrogenase-gene (gGAPDH).

Results

A total of 1176 randomly chosen cattle from five divisions in the Sudano-Sahelian and Guinea Savannah of Cameroon were examined. The overall prevalence of trypanosomes by microscopy was 5.9% (56/953) in contrast to 53.2% (626/1176) when molecular tools were used. This indicated a limited sensitivity of microscopy in subclinical infections with frequently low parasitemia. Three trypanosome species were identified by light microscopy: T. vivax (2.3%), T. brucei (3.7%) and T. congolense (3.0%), whereas five were identified by PCR, namely T. grayi/T. theileri (30.8%), T. vivax (17.7%), T. brucei (14.5%) and T. congolense (5.1%). Unexpected cases of T. grayi (n = 4) and T. theileri (n = 26) were confirmed by sequencing. Phylogenetic analysis of the gGAPDH revealed the presence of T. vivax, clade A and T. vivax clade C, which were co-endemic in the Faro et Deo division.

T. grayi/T. theileri were the predominant species infecting cattle in tsetse free areas. In contrast, T. vivax, T. brucei and T. congolense were more abundant in areas where the Glossina-vectors were present.

Conclusions

The abundance of pathogenic trypanosomes in tsetse infested areas is alarming and even more, the occurrence of T. vivax, T. brucei, T. congolense, T. theileri and T. grayi in tsetse-free areas implies that tsetse control alone is not sufficient to control trypanosomosis in livestock. To implement control measures that reduce the risk of spread in tsetse free areas, close monitoring using molecular tools and a thorough search for alternative vectors of trypanosomes is recommended.

Prevalence of symbionts and trypanosome infections in tsetse flies of two villages of the "Faro and Déo" division of the Adamawa region of Cameroon

Background

Tsetse flies are vectors of human and animal African trypanosomiasis. In spite of many decades of chemotherapy and vector control, the disease has not been eradicated. Other methods like the transformation of tsetse fly symbionts to render the fly refractory to trypanosome infection are being evaluated. The aim of the present study was to evaluate the association between trypanosome infections and the presence of symbionts in these tsetse species. Tsetse flies were trapped in two villages of the “Faro and Déo” Division of the Adamawa region of Cameroon. In the field, tsetse fly species were identified and their infection by trypanosomes was checked by microscopy. In the laboratory, DNA was extracted from their midguts and the presence of symbionts (Sodalis glossinidius and Wolbachia sp.) and trypanosomes was checked by PCR. Symbionts/trypanosomes association tests were performed.

Results

Three tsetse fly species including Glossina tachinoides (90.1%), Glossina morsitans submorsitans (9.4%) and Glossina fuscipes fuscipes (0.5%) were caught. In all the population we obtained an occurrence rate of 37.2% for Sodalis glossinidius and 67.6% for Wolbachia irrespective to tsetse flies species. S. glossinidius and Wolbachia sp. occurrence rates were respectively 37 and 68% for G. tachinoides and 28.6 and 59.5% for G. m. submorsitans. Between Golde Bourle and Mayo Dagoum significant differences were observed in the prevalence of symbionts. Prevalence of trypanosomes were 34.8% for Glossina tachinoides and 40.5% for Glossina morsitans submorsitans. In G. tachinoides, the trypanosome infection rates were 11, 2.6 and 13.7%, respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type. In G. m. submorsitans, these infection rates were 16.7, 9.5 and, 2.4% respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type.

Conclusions

The rate of tsetse fly infection by trypanosomes was low compared to those obtained in HAT foci of south Cameroon, and this rate was not statistically linked to the rate of symbiont occurrence. This study allowed to show for the first time the presence of Wolbachia sp. in the tsetse fly sub-species Glossina morsitans submorsitans and Glossina tachinoides.

A meta-analysis of the prevalence of bovine trypanosomiasis in some African countries from 2000 to 2018

Bovine trypanosomiasis is a disease of cattle. In sub-Saharan Africa, the disease mean prevalence estimates are unknown in most endemic countries. We therefore performed a meta-analysis with the aim of estimating national mean prevalence of bovine trypanosomiasis in endemic countries across sub-Saharan Africa. Relevant articles reporting bovine trypanosomiasis prevalence were retrieved through systematic literature search and scanning of articles reference-lists. Eligibility criteria included that articles reported sample size, prevalence, and diagnostic technique adopted. Overall, data from 180 eligible articles from 19 countries satisfied the inclusion criteria. Meta-analysis of prevalence data based on the random-effects model resulted in an overall mean prevalence of 15.10% (95% CI: 13.22-17.08). National prevalence estimates were generally high except those of Benin and Senegal where estimates ranked below 10.00%. Significant heterogeneity (I² = 98.75%. p = <0.0001) was noted between studies, and univariate meta-regression analysis identified choice of diagnostic method being major contributor to observed heterogeneity (R² = 36.37%); while country of study (R² = 9.57%) and sample size (R² = 3.47%) had marginal effect on heterogeneity. In spite of past and ongoing control activities, bovine trypanosomiasis remains highly prevalent in most endemic sub-Saharan African countries. Nevertheless, dearth of epidemiological data in some countries and the use of less sensitive diagnostic tools limit reliable estimation of the disease prevalence. Therefore, there is the need to intensify efforts in aspects of surveillance and increased application of molecular diagnostic tool(s) across endemic locations as this would raise the chances of achieving a near-accurate estimate of the disease prevalence which is the first step to attempting eradication.

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.

Molecular screening of tsetse flies and cattle reveal different Trypanosoma species including T. grayi and T. theileri in northern Cameroon

BACKGROUND

African trypanosomes are mainly transmitted through the bite of tsetse flies (Glossina spp.). The present study investigated the occurrence of pathogenic trypanosomes in tsetse flies and cattle in tsetse fly-infested areas of Northern Cameroon.

RESULTS

Trypanosomes were identified using nested polymerase chain reaction (PCR) analysis of internal transcribed spacer 1 (ITS1) region, both by size estimation and sequencing of PCR products. Apparent density indices recorded in Gamba and Dodeo were 3.1 and 3.6 tsetse flies per trap and day, respectively. Trypanosoma prevalence infection rate for the tsetse fly gut (40%) and proboscis (19%) were recorded. Among the flies where trypanosomes were detected in the gut, 41.7% were positive for T. congolense and 14.6% for T. brucei ssp., whereas in the proboscis 36% harboured T. congolense and 62% contained T. vivax. T. grayi was highly prevalent in tsetse fly gut (58%). The most common mixed infections were the combination of T. congolense and T. grayi. Trypanosome prevalence rate in cattle blood was 6%. Among these, T. vivax represented 26%, T. congolense 35%, T. brucei ssp. 17% and T. theileri 17% of the infections. Surprisingly, in one case T. grayi was found in cattle. The mean packed cell volume (PCV) of cattle positive for trypanosomes was significantly lower (24.1 ± 5.6%; P < 0.05) than that of cattle in which trypanosomes were not detected (27.1 ± 4.9%). Interestingly, the occurrence of T. theileri or T. grayi DNA in cattle also correlated with low PCV at pathological levels.

CONCLUSION

This molecular epidemiological study of Trypanosoma species in Northern Cameroon revealed active foci of trypanosomes in Dodeo and Gamba. These findings are relevant in assessing the status of trypanosomosis in these regions and will serve as a guide for setting the priorities of the government in the control of the disease.

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.

Past and Ongoing Tsetse and Animal Trypanosomiasis Control Operations in Five African Countries: A Systematic Review

BACKGROUND

Control operations targeting Animal African Trypanosomiasis and its primary vector, the tsetse, were covering approximately 128,000 km2 of Africa in 2001, which is a mere 1.3% of the tsetse infested area. Although extensive trypanosomiasis and tsetse (T&T) control operations have been running since the beginning of the 20th century, Animal African Trypanosomiasis is still a major constraint of livestock production in sub-Saharan Africa.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a systematic review of the existing literature describing T&T control programmes conducted in a selection of five African countries, namely Burkina Faso, Cameroon, Ethiopia, Uganda and Zambia, between 1980 and 2015. Sixty-eight documents were eventually selected from those identified by the database search. This was supplemented with information gathered through semi-structured interviews conducted with twelve key informants recruited in the study countries and selected based on their experience and knowledge of T&T control. The combined information from these two sources was used to describe the inputs, processes and outcomes from 23 major T&T control programmes implemented in the study countries. Although there were some data gaps, involvement of the target communities and sustainability of the control activities were identified as the two main issues faced by these programmes. Further, there was a lack of evaluation of these control programmes, as well as a lack of a standardised methodology to conduct such evaluations.

CONCLUSIONS/SIGNIFICANCE

Past experiences demonstrated that coordinated and sustained control activities require careful planning, and evidence of successes, failures and setbacks from past control programmes represent a mine of information. As there is a lack of evaluation of these programmes, these data have not been fully exploited for the design, analyses and justification of future control programmes.

A longitudinal survey of African animal trypanosomiasis in domestic cattle on the Jos Plateau, Nigeria: prevalence, distribution and risk factors

BACKGROUND

Trypanosomiasis is a widespread disease of livestock in Nigeria and a major constraint to the rural economy. The Jos Plateau, Nigeria was free from tsetse flies and the trypanosomes they transmit due to its high altitude and the absence of animal trypanosomiasis attracted large numbers of cattle-keeping pastoralists to inhabit the plateau. The Jos Plateau now plays a significant role in the national cattle industry, accommodating approximately 7% of the national herd and supporting 300,000 pastoralists and over one million cattle. However, during the past two decades tsetse flies have invaded the Jos Plateau and animal trypanosomiasis has become a significant problem for livestock keepers.

METHODS

In 2008 a longitudinal two-stage cluster survey on the Jos Plateau. Cattle were sampled in the dry, early wet and late wet seasons. Parasite identification was undertaken using species-specific polymerase chain reactions to determine the prevalence and distribution bovine trypanosomiasis. Logistic regression was performed to determine risk factors for disease.

RESULTS

The prevalence of bovine trypanosomiasis (Trypanosoma brucei brucei, Trypanosoma congolense savannah, Trypanosoma vivax) across the Jos Plateau was found to be high at 46.8% (39.0 - 54.5%) and significant, seasonal variation was observed between the dry season and the end of the wet season. T. b. brucei was observed at a prevalence of 3.2% (1% - 5.5%); T. congolense at 27.7% (21.8% - 33.6%) and T. vivax at 26.7% (18.2% - 35.3%). High individual variation was observed in trypanosomiasis prevalence between individual villages on the Plateau, ranging from 8.8% to 95.6%. Altitude was found to be a significant risk factor for trypanosomiasis whilst migration also influenced risk for animal trypanosomiasis.

CONCLUSIONS

Trypanosomiasis is now endemic on the Jos Plateau showing high prevalence in cattle and is influenced by seasonality, altitude and migration practices. Attempts to successfully control animal trypanosomiasis on the Plateau will need to take into account the large variability in trypanosomiasis infection rates between villages, the influence of land use, and husbandry and management practices of the pastoralists, all of which affect the epidemiology of the disease.

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.

Prevalence of bovine trypanosomosis and its vectors in two districts of East Wollega Zone, Ethiopia

Trypanosomosis is a parasitic disease that causes serious economic losses in livestock, especially in sub-Saharan countries. This study was conducted from October 2010 to March 2011 in the Diga and Sasiga districts of the East Wollega zone in western Ethiopia to determine the prevalence of bovine trypanosomosis and its vectors. A total of 386 blood samples were collected from randomly selected animals. Packed cell volume (PCV) was determined and samples were examined for the presence of trypanosomes using the buffy coat technique. Out of 386 blood samples, 8.55% tested positive for trypanosomes. The majority of the infections were caused by Trypanosoma congolense (72.73%), followed by Trypanosoma vivax (27.27%). There were no statistically significant differences (p &gt; 0.05) between districts, altitudes, sexes and ages, but the prevalence was significantly higher (p &lt; 0.05) in cattle which were in poor body condition. The mean PCV value of infected animals (21.45 ± 3.62 s.d.) was significantly lower (p &lt; 0.05) than that of non-infected animals (26.60 ± 4.60 s.d.). A total of 1151 flies were caught by deploying 21 monoconical shaped traps. Of these flies, 822 (71.42%) were Glossina, whilst the remaining flies were either Stomoxys (17.20%) or Tabanus (11.38%). The overall apparent densities of tsetse and biting flies were 1.45 and 0.58 flies per trap per day, respectively. In conclusion, this study confirmed that trypanosomes and their vectors are prevalent and still pose a threat to cattle production in the area. Therefore, proper strategies have to be designed and implemented to minimise their effect on livestock production.

Trypanosoma vivax, T. congolense "forest type" and T. simiae: prevalence in domestic animals of sleeping sickness foci of Cameroon

In order to better understand the epidemiology of Human and Animal trypanosomiasis that occur together in sleeping sickness foci, a study of prevalences of animal parasites (Trypanosoma vivax, T. congolense "forest type", and T. simiae) infections was conducted on domestic animals to complete the previous work carried on T. brucei gambiense prevalence using the same animal sample. 875 domestic animals, including 307 pigs, 264 goats, 267 sheep and 37 dogs were sampled in the sleeping sickness foci of Bipindi, Campo, Doumé and Fontem in Cameroon. The polymerase chain reaction (PCR) based method was used to identify these trypanosome species. A total of 237 (27.08%) domestic animals were infected by at least one trypanosome species. The prevalence of T. vivax, T. congolense "forest type" and T. simiae were 20.91%, 11.42% and 0.34% respectively. The prevalences of 7 vivax and T. congolense "forest type" differed significantly between the animal species and between the foci (p < 0.0001); however, these two trypanosomes were found in all animal species as well as in all the foci subjected to the study. The high prevalences of 7 vivax and T congolense "forest type" in Bipindi and Fontem-Center indicate their intense transmission in these foci.

Survey on bovine trypanosomosis and its vector in Metekel and Awi zones of Northwest Ethiopia

A cross-sectional study was conducted between November 2009 and December 2009 in the riverbank of Abay river tributaries, located in three districts of Awi and Metekel zones, Northwest Ethiopia. The prevalence of bovine trypanosomosis, associated risk factors and distribution as well as vector identification in the study area were considered. Blood samples were collected from 540 randomly selected local (zebu) breed of cattle in nine peasant associations of three districts and the assumed risk factors were recorded. The collected samples were examined using hematological and parasitological techniques. In this study, sixty-seven animals (12.42%) were infected with different species of trypanosomes. Most of the infections were due to T. congolense (77.6%) followed by T. vivax (14.9%), T. brucei (6.0%) and mixed infection of T. congolense and T. vivax (1.5%). There was no statistical significance (p>0.05) between sex, age and coat color of skin, but significant differences were observed in body condition, altitude and districts (p<0.05). Mean PCV value of infected (19.42%) and non-infected (24.13%) group of animals had significant variation; and mean PCV value of poor body condition was significantly different (p<0.001) from good body condition. A total of 3072 tsetse flies of riverine species or palpalis group (Glossina tachinoides) and biting flies were caught, of these 2792 (90.9%) were tsetse flies and the remaining were Stomoxys and Tabanus. The overall apparent densities of tsetse and biting flies were 6.49 and 0.65flies/trap/day, respectively and the difference was significant (p<0.05). The study revealed that bovine trypanosomosis is more prevalent in low land and in poor body condition animals in the study area. Tsetse distribution also coincides with altitude, where there was high tsetse catch in low land, but none in mid land. Therefore, prompt control strategy has to be designed and implemented in the area to minimize the distribution of tsetse as well as trypanosomosis prevalence.

Seasonal distribution and abundance of tsetse flies (Glossina spp.) in the Faro and Deo Division of the Adamaoua Plateau in Cameroon

Ten years after the large-scale tsetse control campaigns in the important cattle rearing areas of the Faro and Deo Division of the Adamaoua Plateau in Cameroon, the seasonal distribution and abundance of tsetse flies (Glossina spp.) were determined. During a period of 12 consecutive months (January-December 2005), the tsetse population was monitored along four trap transects consisting of a total of 32 traps and two flyround transects traversing the study area, which comprised the tsetse-infested valley, a buffer zone and the supposedly tsetse-free plateau. Throughout the study period, a total of 2195 Glossina morsitans submorsitans and 23 Glossina tachinoides were captured in the traps and 1007 G. m. submorsitans (78.8% male flies) were captured along the flyround transects. All G. tachinoides and almost all G. m. submorsitans were captured in the valley. Five G. m. submorsitans were captured in traps located in the buffer zone, whereas no flies were captured in traps located on the plateau. The index of apparent abundance (IAA) of G. m. submorsitans was substantially higher in the areas close to game reserves. In the remaining part of the valley, where wildlife is scarce and cattle are present during transhumance (dry season), the IAA of tsetse was substantially lower. In this part of the valley, the abundance of tsetse seemed to be associated with the presence of cattle, with the highest IAA during transhumance when cattle are present and the lowest apparent abundance during the rainy season when cattle have moved to the plateau. It is concluded that the distribution of tsetse in a large part of the valley undergoes substantial seasonal changes depending on the presence or absence of cattle. The repercussions of those findings for the control of tsetse in the valley and the probability of reinvasion of the plateau are discussed.