Animal trypanosomosis in clinically healthy cattle of north Cameroon: epidemiological implications

The internal transcribed spacer 1 sequence polymorphism brings updates to tsetse species distribution in the northern Cameroon: Importance in planning efficient vector control

Vector control remains one of the best strategies to prevent the transmission of trypanosome infections in humans and livestock and, thus, a good way to achieve the elimination of human African trypanosomiasis and animal African trypanosomiasis. A key prerequisite for the success of any vector control strategy is the accurate identification and correct mapping of tsetse species. In this work, we updated the tsetse fly species identification and distribution in many geographical areas in Cameroon. Tsetse flies were captured from six localities in Cameroon, and their species were morphologically identified. Thereafter, DNA was extracted from legs of each tsetse fly and the length polymorphism of internal transcribed spacer-1 (ITS1) region of each fly was investigated using PCR. ITS1 DNA fragments of each tsetse species were sequenced. The sequences obtained were analysed and compared to those available in GenBank. This enabled to confirm/infirm results of the morphologic identification and then, to establish the phylogenetic relationships between tsetse species. Morphologic features allowed to clearly distinguish all the tsetse species captured in the South Region of Cameroon, that is, Glossina palpalis palpalis, G. pallicera, G. caliginea and G. nigrofusca. In the northern area, G. morsitans submorsitans could also be distinguished from G. palpalis palpalis, G. tachinoides and G. fuscipes, but these three later could not be distinguished with routine morphological characters. The ITS1 length polymorphism was high among most of the studied species and allowed to identify the following similar species with a single PCR, that is, G. palpalis palpalis with 241 or 242 bp and G. tachinoides with 221 or 222 bp, G. fuscipes with 236 or 237 bp. We also updated the old distribution of tsetse species in the areas assessed, highlighting the presence of G. palpalis palpalis instead of G. fuscipes in Mbakaou, or in sympatry with G. morsitans submorsitans in Dodeo (northern Cameroon). This study confirms the presence of G. palpalis palpalis in the Adamawa Region of Cameroon. It highlights the limits of using morphological criteria to differentiate some tsetse species. Molecular tools based on the polymorphism of ITS1 of tsetse flies can differentiate tsetse species through a simple PCR before downstream analyses or vector control planning.

Epidemiological study on cattle trypanosomiasis and its vectors distributions in the Gambella regional state, southwestern Ethiopia

African animal trypanosomosis is a parasitic disease that causes significant economic losses in livestock due to anaemia, loss of condition, emaciation, and mortality. It is a key impediment to increased cattle output and productivity in Ethiopia. Cross-sectional entomological and parasitological studies were performed in the Gambella Region state of southwestern Ethiopia to estimate the prevalence of bovine trypanosomosis, apparent fly density, and potential risk factors. Blood samples were taken from 546 cattle for the parasitological study and analyzed using the buffy coat technique and stained with Giemsa. A total of 189 biconical (89) and NGU (100) traps were deployed in the specified districts for the entomological survey. The overall prevalence of trypanosomosis at the animal level was 5.5% (95% CI: 3.86-7.75). Trypanosoma vivax (50.0%), T. congolense (30.0%), T. brucei (20.0%), and no mixed trypanosome species were found. The prevalence of trypanosomosis was significantly (p < 0.05) affected by altitude, body score conditions, age, mean packed cell volume (PCV), and peasant associations, while sex and coat color had no significant effect. According to the entomological survey results, a total of 2303 flies were captured and identified as tsetse (Glossina pallidipes (5.3%)) and G. fuscipes fuscipes (3.3%) and other biting flies (Tabanus (60.1%) and Stomoxys (31.3%)). In the current study, the overall apparent density was 4.1 flies/trap/day. This study shows that trypanosomosis remains a significant cattle disease in the Gambella regional state even during the dry season. Thus, the findings support the necessity to improve vector and parasite control measures in the area.

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.

Metabolites From Trypanosome-Infected Cattle as Sensitive Biomarkers for Animal Trypanosomosis

Trypanosomes are important global livestock and human pathogens of public health importance. Elucidating the chemical mechanisms of trypanosome-relevant host interactions can enhance the design and development of a novel, next-generation trypanosomosis diagnostics. However, it is unknown how trypanosome infection affects livestock volatile odors. Here, we show that Trypanosoma congolense and Trypanosoma vivax infections induced dihydro-β- ionone and junenol, while abundance of dihydro-α-ionone, phenolics, p-cresol, and 3-propylphenol significantly elevated in cow urine. These biomarkers of trypanosome infection are conserved in cow breath and the urine metabolites of naturally infected cows, regardless of population, diet, or environment differences. Furthermore, treating trypanosome-infected cows reduced the levels of these indicators back to the pre-infection levels. Finally, we demonstrated that the potential of some specific biomarkers of phenolic origin may be used to detect active trypanosome infections, including low-level infections that are not detectable by microscopy. The sensitivity and specificity of biomarkers detection are suited for rapid, robust, and non-invasive trypanosomosis diagnosis under field conditions.

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%.

Risk factors for equine trypanosomosis and hematological analysis of horses in Paraguay

Animal trypanosomosis, caused by Trypanozoon trypanosomes (Trypanosoma evansi and T. equiperdum), and Trypanosoma vivax, is endemic to South American countries and has a negative impact on the livestock industry. However, the risk factors for trypanosomosis in Paraguay remain unknown. This study aimed to determine the risk factors for equine trypanosomosis in Paraguay based on a PCR-based molecular survey and individual horse sampling data. In this study, 739 blood samples were collected from horses in 16 departments of Paraguay between August 2019 and November 2020. To elucidate the risk factors for trypanosome infection, the relationship between trypanosome infection status detected by PCR and the location, sex, age, breed of horses, and season of sample collection was analyzed. There were no significant differences in trypanosome prevalence in horses between the eastern and western regions, ages, or breeds of horses in Paraguay. Sex and season were identified as risk factors for trypanosome infection in horses in Paraguay in the current study. These results suggest that the rainy-summer season, when vectors increase in number and their blood-sucking activity, could be the most important risk factor for trypanosome infection in Paraguay horses. Preventive measures and treatments should be developed to address these factors.

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.

Prevalence of Trypanosome Species in Cattle Near Ruma National Park, Lambwe Valley, Kenya: An Update From the Historical Focus for African Trypanosomosis

The effective control of diseases in areas shared with wildlife depends on the validity of the epidemiologic parameters that guide interventions. Epidemiologic data on animal trypanosomosis in Lambwe valley are decades old, and the recent suspected outbreaks of the disease in the valley necessitate the urgent bridging of this data gap. This cross-sectional study estimated the prevalence of bovine trypanosomosis, identified risk factors, and investigated the occurrence of species with zoonotic potential in Lambwe valley. The area is ~324 km², of which 120 km² is the Ruma National Park. Blood was sampled from the jugular and marginal ear veins of 952 zebu cattle between December 2018 and February 2019 and tested for trypanosomes using the Buffy Coat Technique (BCT) and PCR-High-Resolution Melting (HRM) analysis of the 18S RNA locus. Risk factors for the disease were determined using logistic regression. The overall trypanosome prevalence was 11.0% by BCT [95% confidence interval (CI): 9.0–13.0] and 27.9% by PCR-HRM (95% CI: 25.1–30.8). With PCR-HRM as a reference, four species of trypanosomes were detected at prevalences of 12.7% for T. congolense savannah (95% CI: 10.6–14.8), 7.7% for T. brucei brucei (CI: 6.0–9.4), 8.7% for T. vivax (CI: 6.9–10.5), and 1.3% for T. theileri (CI: 0.6–2.0). About 2.4% of cattle had mixed infections (CI: 1.4–3.41). No human-infective trypanosomes were found. Infections clustered across villages but were not associated with animal age, sex, herd size, and distance from the park. Approximately 85% of infections occurred within 2 km of the park. These findings add to evidence that previous interventions eliminated human trypanosomosis but not bovine trypanosomosis. Risk-tailored intervention within 2 km of Ruma Park, especially in the north and south ends, coupled with stringent screening with molecular tools, could significantly reduce bovine trypanosomosis.

Prevalence and risk factors for trypanosome infection in cattle from communities surrounding the Murchison Falls National Park, Uganda

Background

Bovine trypanosomosis transmitted by tsetse flies is a major constraint to cattle health and productivity in all sub-Saharan countries, including Uganda. The objectives of this study were to determine the prevalence of bovine trypanosomosis and identify its associated risk factors and the species of trypanosomes associated with the disease.

Methodology

A cross-sectional study was conducted around Murchison Falls National Park, Uganda from January 2020 to April 2020. Trypanosomes were detected in blood samples by PCR analysis targeting the internal transcribed spacer 1 (ITS-PCR assays), and trypanosomes in positive blood samples were sequenced.

Results

Of 460 blood samples collected and tested, 136 (29.6%) were positive for trypanosome infections and 324 (70.4%) were negative. The overall trypanosome prevalence was 29.6% (95% confidence interval 25.4–33.8%), attributed to three trypanosome species. Of these three species, Trypanosoma vivax was the most prevalent (n = 130, 28.3%) while the others were detected as mixed infections: T. vivax + Trypanosomacongolense (n = 2, 0.4%) and T. vivax + Trypanosomaevansi (n = 1, 0.2%). There were significant differences in trypanosome prevalence according to sex (χ² = 62, df = 1, P < 0.05), age (χ² = 6.28, df = 2, P = 0.0043) and cattle breed (χ² = 10.61, df = 1, P = 0.001).

Conclusions

Trypanosomosis remains a major limitation to cattle production around Murchison Falls National Park and interventions are urgently needed. In our study, the prevalence of trypanosome infections was high, with T. vivax identified as the most prevalent species. Age, sex and breed of cattle were risk factors for trypanosome infection.

Graphical Abstract

Diversity of tsetse flies and trypanosome species circulating in the area of Lake Iro in southeastern Chad

BACKGROUND

African trypanosomiases are vector-borne diseases that affect humans and livestock in sub-Saharan Africa. Although data have been collected on tsetse fauna as well as trypanosome infections in tsetse flies and mammals in foci of sleeping sickness in Chad, the situation of tsetse fly-transmitted trypanosomes remains unknown in several tsetse-infested areas of Chad. This study was designed to fill this epidemiological knowledge gap by determining the tsetse fauna as well as the trypanosomes infecting tsetse flies in the area of Lake Iro in southeastern Chad.

METHODS

Tsetse flies were trapped along the Salamat River using biconical traps. The proboscis and tsetse body were removed from each fly. DNA was extracted from the proboscis using proteinase K and phosphate buffer and from the tsetse body using Chelex 5%. Tsetse flies were identified by amplifying and sequencing the cytochrome c oxydase I gene of each tsetse fly. Trypanosome species were detected by amplifying and sequencing the internal transcribed spacer 1 of infecting trypanosomes.

RESULTS

A total of 617 tsetse flies were trapped; the apparent density of flies per trap per day was 2. 6. Of the trapped flies, 359 were randomly selected for the molecular identification and for the detection of infecting trypanosomes. Glossina morsitans submorsitans (96.1%) was the dominant tsetse fly species followed by G. fuscipes fuscipes (3.1%) and G. tachinoides (0.8%). Four trypanosome species, including Trypanosoma vivax, T. simiae, T. godfreyi and T. congolense savannah, were detected. Both single infection (56.7%) and mixed infections of trypanosomes (4.6%) were detected in G. m. submorsitans. The single infection included T. simiae (20.5%), T. congolense savannah (16.43%), T. vivax (11.7%) and T. godfreyi (9.8%). The trypanosome infection rate was 61.4% in G. m. submorsitans, 72.7% in G. f. fuscipes and 66.6% in G. tachinoides. Trypanosome infections were more prevalent in tsetse bodies (40.6%) than in the proboscis (16.3%).

CONCLUSION

This study revealed the presence of different tsetse species and a diversity of trypanosomes pathogenic to livestock in the area of Lake Iro. The results highlight the risks and constraints that animal African trypanosomiasis pose to livestock breeding and the importance of assessing trypanosome infections in livestock in this area.

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.

Global distribution, host range and prevalence of Trypanosoma vivax: a systematic review and meta-analysis

BACKGROUND

Trypanosomosis caused by Trypanosoma vivax is one of the diseases threatening the health and productivity of livestock in Africa and Latin America. Trypanosoma vivax is mainly transmitted by tsetse flies; however, the parasite has also acquired the ability to be transmitted mechanically by hematophagous dipterans. Understanding its distribution, host range and prevalence is a key step in local and global efforts to control the disease.

METHODS

The study was conducted according to the methodological recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. A systematic literature search was conducted on three search engines, namely PubMed, Scopus and CAB Direct, to identify all publications reporting natural infection of T. vivax across the world. All the three search engines were screened using the search term Trypanosoma vivax without time and language restrictions. Publications on T. vivax that met our inclusion criteria were considered for systematic review and meta-analysis.

RESULT

The study provides a global database of T. vivax, consisting of 899 records from 245 peer-reviewed articles in 41 countries. A total of 232, 6277 tests were performed on 97 different mammalian hosts, including a wide range of wild animals. Natural infections of T. vivax were recorded in 39 different African and Latin American countries and 47 mammalian host species. All the 245 articles were included into the qualitative analysis, while information from 186 cross-sectional studies was used in the quantitative analysis mainly to estimate the pooled prevalence. Pooled prevalence estimates of T. vivax in domestic buffalo, cattle, dog, dromedary camel, equine, pig, small ruminant and wild animals were 30.6%, 6.4%, 2.6%, 8.4%, 3.7%, 5.5%, 3.8% and 12.9%, respectively. Stratified according to the diagnostic method, the highest pooled prevalences were found with serological techniques in domesticated buffalo (57.6%) followed by equine (50.0%) and wild animals (49.3%).

CONCLUSION

The study provides a comprehensive dataset on the geographical distribution and host range of T. vivax and demonstrates the potential of this parasite to invade other countries out of Africa and Latin America.

Bovine trypanosomosis in upstream and downstream of Ghibe-III hydroelectric dam: parasitological and entomological study, southern Ethiopia

Two-point cross-sectional study design in dry and rainy seasons was employed near Ghibe-III Dam from December 2018 to July 2019. Trypanosomosis prevalence comparison between downstream (Kindodidaye) and upstream (Loma districts), associated risk factors, vector dispersion, identification and vector infection rate considered. Blood sample collected from 1280 cattle from two districts during dry and rainy seasons; the assumed risk factors recorded. Samples were examined using heamatological and parasitological techniques. In this study 9.1% (116/1280) trypanosomosis prevalence recorded. Prevalence was significantly (p < 0.05) different between Kindodidaye (11.7%) and Loma (6.4%). Most of the infections were due to T. congolense (79.3%) followed by T. vivax (17.2%) and T. brucei (2.6%) and one mixed infection recorded. Significant (p < 0.05) difference observed in season, within district and between districts. Among the assumed risk factors: district, season, Kebele and body condition score showed significant (p < 0.05) difference; whereas sex, age, color weren't significantly (p > 0.05) different. Significantly (p < 0.05) low mean PCV observed in infected group, dry season and Kindodidaye district. Entomological survey revealed 1030 tsetse spp. (G. pallidipes and G. fuscipes) and 2045 biting flies mainly Stomoxysis and Tabanus, and other unidentified spp. recorded. Tsetse apparent density were significantly (p < 0.05) high in Kindodidaye and rainy season with value of 5.3 and 7.1 F/T/D, respectively. Out of 182 tsetse fly dissected twenty seven (14.6%) of them were infected. A proportion of 23.0%, 30.8% and 46.2% infection rate recorded in proboscis, salivary gland and mid gut, respectively. The study shows Kindodidaye and rainy season had high trypanosomosis and tsetse apparent density than Loma. The difference might be associated with water reserve created due to Ghibe III hydroelectric dam and this could be a golden opportunity in the area to contribute tsetse control program. Stakeholders' need to aware to use this opportunity before tsetse adapts itself into new environment or niche for their survival.

Molecular identification of diminazene aceturate-resistant strains of Trypanosoma congolense in naturally infected domestic animals of Yoko in the centre region of Cameroon

African animal trypanosomiases (AAT) remain the major constraint for livestock production, agriculture and food security in Africa. Although several control measures have been developed to fight AAT, the use of trypanocides remains the main strategy in most affected poor and rural communities. However, several studies have highlighted drug-resistant-trypanosome infections in many African countries, though this phenomenon is still not well described. This study aims to detect trypanosome species and the molecular profiles of drug-resistant-trypanosomes in naturally infected domestic animals of Yoko in the centre region of southern Cameroon. Therefore, in October 2017, 348 animals were blood sampled. The level of packed cell volume (PCV) was evaluated in each animal and trypanosome infections were investigated with the capillary tube centrifugation technique (CTC). Thereafter, DNA was extracted from blood samples and different trypanosome species were identified by PCR. The resistant/sensitive molecular profiles of trypanosomes for diminazene aceturate (DA) and isometamidium chloride (ISM) were investigated by PCR-RFLP. About 18.4% (64/348) of animals analyzed by PCR were found with trypanosome infections including Trypanosoma vivax, Trypanosoma brucei s.l. and Trypanosoma congolense forest and savannah. Trypanosoma congolense savannah was the predominant species with an infection rate of 15.2%. Between villages, significant (p˂0.0001) differences were found in the overall trypanosome infection rates. No molecular profile for ISM resistant-trypanosomes was identified. Conversely, about 88.9% (40/45) of T. congolense positive samples have shown molecular profiles of DA-resistant strains while the remaining 11.1% (5/45) showed mixed molecular profiles of resistant/sensitive strains. Results showed that the molecular profiles of DA-resistant strains of T. congolense in domestic animals of Yoko were widespread. This data needs to be confirmed by testing in vivo the drug susceptibilities of the trypanosome strains herein detected. In conclusion, appropriate future control measures are required. In addition to the intensification of vector control, ISM is advised for the treatment of animals infected by trypanosomes.

Prevalence of cattle trypanosomosis in slaughterhouses and farms in Benin and impact on hematocrit in cattle

Objective:

The present study aimed to determine the prevalence of bovine trypanosomosis in Benin.

Materials and Methods:

For this purpose, the blood samples were taken from 932 cattle: 573 from slaughterhouses and 359 from the farms of the targeted divisions. After the blood samples, thick drops and blood smears were made. The capillary tubes filled with blood made it possible to determine the hematocrit in cattle.

Results:

The prevalence of trypanosomosis in farms (27.02%) was significantly higher (p < 0.001) than that of animals in slaughterhouses (16.75%). In farms, the prevalence was 38.55% during the rainy season against 16.67% in the dry season (p < 0.001). In slaughterhouses, prevalences were 10.99%, 17.58%, and 21.50%, respectively, in Bohicon, Cotonou/Porto-Novo, and Parakou. Hematocrit in slaughterhouses was 24.17% and 31.44%, respectively, in infested and non-infested animals. In farms, this rate was 22.85% in infested animals and 29.31% in non-infested animals (p < 0.05). Young cattle are more vulnerable to trypanosomosis than older cattle.

Conclusion:

Given the endemic situation of bovine trypanosomosis and its impact on the economy, this knowledge of the health status of cattle will help out to seek ways and alternatives to reduce the damage.

Identification of Candidate Signature Genes and Key Regulators Associated With Trypanotolerance in the Sheko Breed

African animal trypanosomiasis (AAT) is caused by a protozoan parasite that affects the health of livestock. Livestock production in Ethiopia is severely hampered by AAT and various controlling measures were not successful to eradicate the disease. AAT affects the indigenous breeds in varying degrees. However, the Sheko breed shows better trypanotolerance than other breeds. The tolerance attributes of Sheko are believed to be associated with its taurine genetic background but the genetic controls of these tolerance attributes of Sheko are not well understood. In order to investigate the level of taurine background in the genome, we compare the genome of Sheko with that of 11 other African breeds. We find that Sheko has an admixed genome composed of taurine and indicine ancestries. We apply three methods: (i) The integrated haplotype score (iHS), (ii) the standardized log ratio of integrated site specific extended haplotype homozygosity between populations (Rsb), and (iii) the composite likelihood ratio (CLR) method to discover selective sweeps in the Sheko genome. We identify 99 genomic regions harboring 364 signature genes in Sheko. Out of the signature genes, 15 genes are selected based on their biological importance described in the literature. We also identify 13 overrepresented pathways and 10 master regulators in Sheko using the TRANSPATH database in the geneXplain platform. Most of the pathways are related with oxidative stress responses indicating a possible selection response against the induction of oxidative stress following trypanosomiasis infection in Sheko. Furthermore, we present for the first time the importance of master regulators involved in trypanotolerance not only for the Sheko breed but also in the context of cattle genomics. Our finding shows that the master regulator Caspase is a key protease which plays a major role for the emergence of adaptive immunity in harmony with the other master regulators. These results suggest that designing and implementing genetic intervention strategies is necessary to improve the performance of susceptible animals. Moreover, the master regulatory analysis suggests potential candidate therapeutic targets for the development of new drugs for trypanosomiasis treatment.

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.

Leveraging Available Resources and Stakeholder Involvement for Improved Productivity of African Livestock in the Era of Genomic Breeding

The African continent is home to diverse populations of livestock breeds adapted to harsh environmental conditions with more than 70% under traditional systems of management. Animal productivity is less than optimal in most cases and is faced with numerous challenges including limited access to adequate nutrition and disease management, poor institutional capacities and lack of adequate government policies and funding to develop the livestock sector. Africa is home to about 1.3 billion people and with increasing demand for animal proteins by an ever growing human population, the current state of livestock productivity creates a significant yield gap for animal products. Although a greater section of the population, especially those living in rural areas depend largely on livestock for their livelihoods; the potential of the sector remains underutilized and therefore unable to contribute significantly to economic development and social wellbeing of the people. With current advances in livestock management practices, breeding technologies and health management, and with inclusion of all stakeholders, African livestock populations can be sustainably developed to close the animal protein gap that exists in the continent. In particular, advances in gene technologies, and application of genomic breeding in many Western countries has resulted in tremendous gains in traits like milk production with the potential that, implementation of genomic selection and other improved practices (nutrition, healthcare, etc.) can lead to rapid improvement in traits of economic importance in African livestock populations. The African livestock populations in the context of this review are limited to cattle, goat, pig, poultry, and sheep, which are mainly exploited for meat, milk, and eggs. This review examines the current state of livestock productivity in Africa, the main challenges faced by the sector, the role of various stakeholders and discusses in-depth strategies that can enable the application of genomic technologies for rapid improvement of livestock traits of economic importance.

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.

Molecular identification of bovine trypanosomes in relation to cattle sources in southwest Nigeria

Bovine trypanosomosis is a problem in the livestock industry in Nigeria. A longitudinal survey of cattle sampled during the wet and dry seasons was conducted from April 2016 to March 2017. Blood samples were collected by random sampling from 745 cattle in southwest Nigeria and screened for trypanosomes by internal transcribed spacer-polymerase chain reaction (ITS-PCR). Cattle positive for Trypanozoon DNA were further screened with the Rode Trypanozoon antigen type (RoTat) 1.2 PCR and Trypanosoma brucei gambiense glycoprotein (TgsGP) genes for T. evansi and T. b. gambiense respectively. Trypanosome DNA was amplified in 23.8% (95%CI: 20.8-26.9) of cattle with significantly higher prevalence in wet season (95%CI: 22.9-30.8) when compared to the dry season (95%CI: 14.3-23.6). A high prevalence was observed in Fulani cattle farms 54.1% (95%CI: 42.78-64.93%) while the prevalence was lower in institutional farms 14.7% (95%CI: 10.10-20.97%). Trypanosoma vivax was the most prevalent trypanosome observed (11.54% (95%CI: 9.44-14.04%)), followed by T. congolense 8.5% (95%CI: 6.67-10.67%) T. b. brucei 4.8% (95%CI: 3.51-6.62%) and T. evansi 1.74% (95%CI: 1.02-2.96%). Mixed infections were observed in 2.8% (95%CI: 1.85-4.27%) of cattle. Seasonal variation revealed a predominance of T. congolense and T. vivax in wet and dry season, respectively. The high prevalence of Trypanosoma species in cattle indicates a need for expanded surveillance for AAT in southwest Nigeria. Migration, settlement patterns, increased marketing and management types were some of the risk factors identified for AAT.

The Structure of a Conserved Telomeric Region Associated with Variant Antigen Loci in the Blood Parasite Trypanosoma congolense

African trypanosomiasis is a vector-borne disease of humans and livestock caused by African trypanosomes (Trypanosoma spp.). Survival in the vertebrate bloodstream depends on antigenic variation of Variant Surface Glycoproteins (VSGs) coating the parasite surface. In T. brucei, a model for antigenic variation, monoallelic VSG expression originates from dedicated VSG expression sites (VES). Trypanosoma brucei VES have a conserved structure consisting of a telomeric VSG locus downstream of unique, repeat sequences, and an independent promoter. Additional protein-coding sequences, known as “Expression Site Associated Genes (ESAGs)”, are also often present and are implicated in diverse, bloodstream-stage functions. Trypanosoma congolense is a related veterinary pathogen, also displaying VSG-mediated antigenic variation. A T. congolense VES has not been described, making it unclear if regulation of VSG expression is conserved between species. Here, we describe a conserved telomeric region associated with VSG loci from long-read DNA sequencing of two T. congolense strains, which consists of a distal repeat, conserved noncoding elements and other genes besides the VSG; although these are not orthologous to T. brucei ESAGs. Most conserved telomeric regions are associated with accessory minichromosomes, but the same structure may also be associated with megabase chromosomes. We propose that this region represents the T. congolense VES, and through comparison with T. brucei, we discuss the parallel evolution of antigenic switching mechanisms, and unique adaptation of the T. brucei VES for developmental regulation of bloodstream-stage genes. Hence, we provide a basis for understanding antigenic switching in T. congolense and the origins of the African trypanosome VES.

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.

New insights from Gorongosa National Park and Niassa National Reserve of Mozambique increasing the genetic diversity of Trypanosoma vivax and Trypanosoma vivax-like in tsetse flies, wild ungulates and livestock from East Africa

BACKGROUND

Trypanosoma (Duttonella) vivax is a major pathogen of livestock in Africa and South America (SA), and genetic studies limited to small sampling suggest greater diversity in East Africa (EA) compared to both West Africa (WA) and SA.

METHODS

Multidimensional scaling and phylogenetic analyses of 112 sequences of the glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) gene and 263 sequences of the internal transcribed spacer of rDNA (ITS rDNA) were performed to compare trypanosomes from tsetse flies from Gorongosa National Park and Niassa National Reserve of Mozambique (MZ), wild ungulates and livestock from EA, and livestock isolates from WA and SA.

RESULTS

Multidimensional scaling (MDS) supported Tvv (T. vivax) and TvL (T. vivax-like) evolutionary lineages: 1) Tvv comprises two main groups, TvvA/B (all SA and WA isolates plus some isolates from EA) and TvvC/D (exclusively from EA). The network revealed five ITS-genotypes within Tvv: Tvv1 (WA/EA isolates), Tvv2 (SA) and Tvv3-5 (EA). EA genotypes of Tvv ranged from highly related to largely different from WA/SA genotypes. 2) TvL comprises two gGAPDH-groups formed exclusively by EA sequences, TvLA (Tanzania/Kenya) and TvLB-D (MZ). This lineage contains more than 11 ITS-genotypes, seven forming the lineage TvL-Gorongosa that diverged from T. vivax Y486 enough to be identified as another species of the subgenus Duttonella. While gGAPDH sequences were fundamental for classification at the subgenus, major evolutionary lineages and species levels, ITS rDNA sequences permitted identification of known and novel genotypes.

CONCLUSIONS

Our results corroborate a remarkable diversity of Duttonella trypanosomes in EA, especially in wildlife conservation areas, compared to the moderate diversity in WA. Surveys in wilderness areas in WA may reveal greater diversity. Biogeographical and phylogenetic data point to EA as the place of origin, diversification and spread of Duttonella trypanosomes across Africa, providing relevant insights towards the understanding of T. vivax evolutionary history.

Bovine trypanosomosis and vector density in Omo-Ghibe tsetse belt, South Ethiopia

African animal trypanosomosis (AAT) is a parasitic disease that causes serious economic losses in livestock from anemia, loss of condition, emaciation and death in untreated cases. It is one of the major constraints to improved livestock production and productivity in Ethiopia. Entomological and parasitological surveys were conducted in the Omo-Ghibe tsetse belt of south Ethiopia to estimate the prevalence of bovine trypanosomosis and the apparent tsetse density (AD), and identify the potential risk factors. For the parasitological study, blood samples were collected from 1508 cattle sampled from 11 districts and assayed using the buffy coat technique and Giemsa-stained thin smears. For the entomological survey, a total of 216 biconical and NGU traps were deployed in all districts. The overall animal-level prevalence of trypanosomosis was 7.8% (95% CI: 6.5, 9.3). The trypanosome species identified were Trypanosoma congolense (75.4%), T. vivax (20.3%), T. brucei brucei (1.7%) and mixed T. congolense/T. vivax (2.6%). Regarding the entomological survey result, a total of 2243 tsetse flies were captured which identified to be Glossina pallidipes (85.1%) and G. f. fuscipes (14.9%). Besides, other biting flies of the genus Stomoxys (n=146) and Tabanus (n=17) were also trapped. The AD noted in the present study was 3.5 flies/trap/day. Both the prevalence of trypanosomosis and AD of tsetse flies were significantly (p<0.05) influenced by altitude. The prevalence of trypanosomosis was also significantly (p<0.05) associated with poor body condition score, black coat color and lower mean packed cell volume while no significant prevalence difference was noted along with age and sex category. In conclusion, the present study suggested that trypanosomosis is an important disease of cattle in the Omo-Ghibe tsetse belt in dry season. The disease is mainly caused by the most pathogenic T. congolense and transmission is predominantly by tsetse flies, particularly G. pallidipes. The study warrants the need for strengthening the vector and parasite control interventions in the area.