PREVALENCE OFTHEILERIA EQUIANDBABESIA CABALLIAS WELL AS THE IDENTIFICATION OF ASSOCIATED TICKS IN SYMPATRIC GREVY'S ZEBRAS (EQUUS GREVYI) AND DONKEYS (EQUUS AFRICANUS ASINUS) IN NORTHERN KENYA

Abstract

ABSTRACT:The role of equine piroplasmosis as a factor in the population decline of the Grevy's zebra is not known. We determined the prevalence of Babesia caballi and Theileria equi in cograzing Grevy's zebras (Equus grevyi) and donkeys (Equus africanus asinus) in northern Kenya and identified the associated tick vectors. Blood samples were taken from 71 donkeys and 16 Grevy's zebras from March to May 2011. A nested PCR reaction using 18s ribosomal (r)RNA primers on 87 blood spots showed 72% (51/71; 95% confidence interval [CI] 60.4-81.0%) of donkeys and 100% (16/16; 95% CI, 77.3-100%) of Grevy's zebras were T. equi positive. No samples were positive for B. caballi. Sequence comparison using the National Center for Biotechnology Information's basic local alignment search tool identified homologous 18s rRNA sequences with a global geographic spread. The T. equi-derived sequences were evaluated using Bayesian approaches with independent Metropolis-coupled Markov chain Monte Carlo runs. The sequences clustered with those found in Sudan, Croatia, Mongolia, and the US, with statistical support greater than 80% for the two main clades. Hyalomma tick species were found on both donkeys and Grevy's zebras, whereas Rhipicephalus pulchellus was found exclusively on Grevy's zebras and Hyalomma marginatum rupfipes on donkeys. The prevalence of T. equi was 100% in Grevy's zebras and 72% in donkeys with common tick vectors identified. Our results suggest that donkeys and Grevy's zebras can be asymptomatic carriers and that piroplasmosis is endemic in the study area.

A field survey for the seroprevalence of Theileria equi and Babesia caballi in donkeys from Nuu Division, Kenya

“…Previous studies on donkeys have reported a wide range in the value of (sero)prevalence, this particular study was on the higher side of the range reported. Reported T. equi true (sero)prevalence in donkeys range from approximately 2 to 85% (Turnbull et al, 2002;Chahan et al, 2006;Acici et al, 2008;Machado et al, 2012;Garcia-Bocanegra et al, 2013;Gizachew et al, 2013;Salim et al, 2013) and was similar to the work of Hawkins et al (2015) who found a prevalence of 72% (95% CI: 60.4-81.0%) using PCR. Scrutiny of prevalence values from previous studies is, however, limited due to their unique study designs and the effect of external factors such as husbandry (Kouam et al, 2010a;Garcia-Bocanegra et al, 2013).…”

“…The bulk of published literature describes endemicity in horses leaving the epidemiology of piroplasmosis in donkeys poorly understood despite the species' carrier state potential (Chahan et al, 2006;Kumar et al, 2009;Machado et al, 2012;Gizachew et al, 2013, Hawkins et al, 2015. Studies on equine piroplasmosis in Kenyan donkeys have been previously conducted by Vranova et al (2011) andHawkins et al (2015).…”

“…One possibility that could explain this is a generally low prevalence or complete absence of B. caballi infective ticks in the population. Recent work in northern Kenya found no evidence of B. caballi infection in donkeys or zebras (Hawkins et al, 2015) using a nested PCR reaction targeting the 18s ribosomal (r)RNA gene. The other explanation would be a failure of the diagnostic test to detect the particular strain(s) of B. caballi in the sample.…”

“…Studies on equine piroplasmosis in Kenyan donkeys have been previously conducted by Vranova et al (2011) andHawkins et al (2015). Kenya recorded a 64% increase in the national donkey population between the years 1999-2009.…”

Why the Donkey Did Not Go South: Disease as a Constraint on the Spread of Equus asinus into Southern Africa

“…Horses at least can remain carriers of B. caballi for up to 4 years after initial infection (Holbrook et al 1973). All three species of zebra have also been identified as carriers (Lampen et al 2009;Hawkins et al 2015), and T. equi is likely to have first evolved as an infection of zebras before affecting other equids ).…”