Patterns of helminth infection in Kenyan elephant populations

Background: The dynamics of helminth infection in African elephant populations are poorly known. We examined the efects of age, sex, social structure and the normalized diference vegetation index (NDVI) as primary drivers of infection patterns within and between elephant populations. Methods: Coprological methods were used to identify helminths and determine infection patterns in distinct elephant populations in Maasai Mara National Reserve, Tsavo East National Park, Amboseli National Park and LaikipiaSamburu Ecosystem. Gaussian fnite mixture cluster analyses of egg dimensions were used to classify helminth eggs according to genera. Generalized linear models (GLM) and Chi-square analyses were used to test for variation in helminth infection patterns and to identify drivers in elephant populations. Results: Helminth prevalence varied signifcantly between the studied populations. Nematode prevalence (96.3%) was over twice as high as that of trematodes (39.1%) in elephants. Trematode prevalence but not nematode prevalence varied between populations. Although we found no associations between helminth infection and elephant social groups (male vs family groups), the median helminth egg output (eggs per gram, epg) did vary between social groups: family groups had signifcantly higher median epg than solitary males or males in bachelor groups. Young males in mixed sex family groups had lower epg than females when controlling for population and age; these differences, however, were not statistically signifcant. The average NDVI over a three-month period varied between study locations. Cluster analyses based on egg measurements revealed the presence of Protofasciola sp., Brumptia sp., Murshidia sp., Quilonia sp. and Mammomonogamus sp. GLM analyses showed that the mean epg was positively infuenced by a three-month cumulative mean NDVI and by social group; female social groups had higher epg than male groups. GLM analyses also revealed that epg varied between elephant populations: Samburu-Laikipia elephants had a higher and Tsavo elephants a lower epg than Amboseli elephants. Conclusions: Elephants had infection patterns characterized by within- and between-population variation in prevalence and worm burden. Sociality and NDVI were the major drivers of epg but not of helminth prevalence. Gastrointestinal parasites can have a negative impact on the health of wild elephants, especially during resource scarcity. Thus, our results will be important when deciding intervention strategies.This research was funded by the Kenya Wildlife Service and the Department of Animal Pathology, Veterinary Faculty, University of Santiago de Compostela, Lugo, SpainS

Epidemiology of Theileria bicornis among black and white rhinoceros metapopulation in Kenya

[Background] A huge effort in rhinoceros conservation has focused on poaching and habitat loss as factors leading to the dramatic declines in the endangered eastern black rhinoceros (Diceros bicornis michaeli) and the southern white rhinoceros (Ceratotherium simum simum). Nevertheless, the role disease and parasite infections play in the mortality of protected populations has largely received limited attention. Infections with piroplasmosis caused by Babesia bicornis and Theileria bicornis has been shown to be fatal especially in small and isolated populations in Tanzania and South Africa. However, the occurrence and epidemiology of these parasites in Kenyan rhinoceros is not known.[Results] Utilizing 18S rRNA gene as genetic marker to detect rhinoceros infection with Babesia and Theileria, we examined blood samples collected from seven rhinoceros populations consisting of 114 individuals of black and white rhinoceros. The goal was to determine the prevalence in Kenyan populations, and to assess the association of Babesia and Theileria infection with host species, age, sex, location, season and population mix (only black rhinoceros comparing to black and white rhinoceros populations). We did not detect any infection with Babesia in the sequenced samples, while the prevalence of T. bicornis in the Kenyan rhinoceros population was 49.12% (56/114). White rhinoceros had significantly higher prevalence of infection (66%) compared to black rhinoceros (43%). The infection of rhinoceros with Theileria was not associated with animal age, sex or location. The risk of infection with Theileria was not higher in mixed species populations compared to populations of pure black rhinoceros.[Conclusion] In the rhinoceros studied, we did not detect the presence of Babesia bicornis, while Theileria bicornis was found to have a 49.12% prevalence with white rhinoceros showing a higher prevalence (66%) comparing with black rhinoceros (43%). Other factors such as age, sex, location, and population mix were not found to play a significant role.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe

Whole genome phylogenetic investigation of a West Nile virus strain isolated from a tick sampled from livestock in north eastern Kenya

BACKGROUND:West Nile virus (WNV) has a wide geographical distribution and has been associated to cause neurological disease in humans and horses. Mosquitoes are the traditional vectors for WNV; however, the virus has also been isolated from tick species in North Africa and Europe which could be a means of introduction and spread of the virus over long distances through migratory birds. Although WNV has been isolated in mosquitoes in Kenya, paucity of genetic and pathogenicity data exists. We previously reported the isolation of WNV from ticks collected from livestock and wildlife in Ijara District of Kenya, a hotspot for arbovirus activity. Here we report the full genome sequence and phylogenetic investigation of their origin and relation to strains from other regions. METHODS: A total of 10,488 ticks were sampled from animal hosts, classified to species and processed in pools of up to eight ticks per pool. Virus screening was performed by cell culture, RT-PCR and sequencing. Phylogenetic analysis was carried out to determine the evolutionary relationships of our isolate. RESULTS: Among other viruses, WNV was isolated from a pool of Rhipicephalus pulchellus sampled from cattle, sequenced and submitted to GenBank (Accession number: KC243146). Comparative analysis with 27 different strains revealed that our isolate belongs to lineage 1 and clustered relatively closely to isolates from North Africa and Europe, Russia and the United States. Overall, Bayesian analysis based on nucleotide sequences showed that lineage 1 strains including the Kenyan strain had diverged 200years ago from lineage 2 strains of southern Africa. Ijara strain collected from a tick sampled on livestock was closest to another Kenyan strain and had diverged 20years ago from strains detected in Morocco and Europe and 30years ago from strains identified in the USA. CONCLUSION: To our knowledge, this is the first characterized WNV strain isolated from R. pulchellus. The epidemiological role of this tick in WNV transmission and dissemination remains equivocal but presents tick verses mosquito virus transmission has been neglected. Genetic data of this strain suggest that lineage 1 strains from Africa could be dispersed through tick vectors by wild migratory birds to Europe and beyond

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2017年2月2日(木) 於:早稲田大学 小野記念講

Traumatic myiasis in free-ranging eland, reported from Kenya

Abstract Background For centuries, immature stages of Dipterans have infested humans and animals, resulting in a pathological condition referred to as myiasis. Myiases are globally distributed but they remain neglected diseases in spite of the great medical and veterinary importance. Moreover, there is a paucity of information on the clinical-pathology and/or epidemiology of the infestation, especially in African free ranging wildlife. Findings In the present study we report for the first time an outbreak of traumatic cutaneous myiasis (caused by Old World screwworm, Chrysomyia bezziana and blowfly, Lucilia sp.) in free-ranging common elands (Taurotragus oryx). The infestation affected both animal sexes and different age classes, and had a negative impact on individual fitness as well as the overall health. Severely affected individuals were euthanized, while others were clinically treated, and apparently recovered. Conclusions This study indicates that myiasis-causing flies still exist in Kenya and are able to cause severe outbreaks of clinical cutaneous myiasis in wild animals. The status of these parasites in Kenya, which are of zoonotic potential, are either unknown or neglected.Peer Reviewe

Data from: Illegal tusk harvest and the decline of tusk size in the African elephant

Harvesting of wild populations can cause the evolution of morphological, behavioral, and life history traits that may compromise natural or sexual selection. Despite the vulnerability of large mammals to rapid population decline from harvesting, the evolutionary effects of harvesting on mega-fauna have received limited attention. In elephants, illegal ivory harvesting disproportionately affects older age classes and males because they carry large tusks, but its' effects on tusk size for age or tusk size for stature are less understood. We tested whether severe historical elephant harvests eliminated large tuskers among survivors and whether elephants born thereafter had smaller tusks. Adjusting for the influence of shoulder height – a metric strongly correlated with body size and age and often used as a proxy for age – we compared tusk size for elephants sampled in 1966–1968, prior to severe ivory harvesting in the late 1970s and early 1980s, with tusk size of survivors and elephants born during population recovery in the mid-1990s. In a regional population, tusk length declined by ˜21% in male and by ˜27% in female elephants born during population recovery, while tusk length declined by 22% in males and 37% in females among survivors. Tusk circumference at lip declined by 5% in males but not in females born during population recovery, whereas tusk circumference reduced by 8% in male and by 11% in female survivors. In a single subpopulation, mean tusk length at mean basal tusk circumference declined by 12.4% in males and 21% in females. Tusk size varied between elephant social groups. Tusk homogeneity within social groups and the often high genetic similarity within social groups suggest that tusk size may be heritable. Our findings support a hypothesis of selection of large tuskers by poachers as a driver of the decline in tusk size for age proxy and contemporary tusk evolution in African elephants