Abstract
BackgroundEquine trypanosomiasis is a severe and prevalent disease that has the greatest impact globally upon working equids due to its distribution across lower income countries. Morbidity and mortality rates are high; disease management strategies in endemic regions are ineffective and cost prohibitive. Individual variation in disease phenotype in other species suggests host factors could reveal novel treatment and control targets but has not been investigated in equids.MethodsA prospective clinical evaluation of equines presenting for a free veterinary examination was performed in hyperendemic villages in The Gambia. Age, body condition score and body weight were estimated by validated methods, and haematocrit and total protein concentration measured. Animals fulfilling 2 out of 5 clinical inclusion criteria (anaemia, poor body condition, pyrexia, history of abortion, oedema) for a diagnosis of trypanosomiasis received trypanocidal treatment with follow-up at 1 and 2 weeks. Blood samples underwent PCR analysis with specific Trypanosoma spp. primers and results were compared to the subject’s clinical and clinicopathological features. A mixed effects generalised linear model was generated to evaluate the association of infection status with degree of pyrexia and anaemia.ResultsMorbidity was high within examined (n = 641) and selected (n = 247) study populations. PCR status was not associated with a defined disease phenotype; there was intra- and inter-species variability. Donkeys were more frequently Trypanosoma spp.-positive (P < 0.001) and febrile (P < 0.001) than horses, but infected horses were more anaemic (P < 0.001), and in poorer body condition (P < 0.001) than donkeys. Sex was correlated to disease phenotype: males were more anaemic (P = 0.03) and febrile (P < 0.001). Haemoparasite co-infections were more common than a single infection.ConclusionsThere was evidence of diversity in trypanosomiasis clinical signs plus variable disease phenotypes within equid subpopulations that warrant further investigation. The complex co-infection profile of field cases requires greater consideration to optimise disease management.
Highlights
Equine trypanosomiasis is a severe and prevalent disease that has the greatest impact globally upon working equids due to its distribution across lower income countries
Individual variation in disease phenotype in other species suggests that host factors could reveal novel treatment and control targets [23,24,25]
A detailed history following a standardised format was obtained via Gambia Horse and Donkey Trust staff acting as translators
Summary
Equine trypanosomiasis is a severe and prevalent disease that has the greatest impact globally upon working equids due to its distribution across lower income countries. Individual variation in disease phenotype in other species suggests host factors could reveal novel treatment and control targets but has not been investigated in equids. Infectious diseases are a major inhibitor of welfare and productivity in this population [1, 9,10,11] and equine trypanosomiasis is a priority disease with almost global distribution for which strategies are required to improve diagnosis, management and treatment [10]. Individual variation in disease phenotype in other species suggests that host factors could reveal novel treatment and control targets [23,24,25]. Asymptomatic or subclinical individuals constitute a unique resource to investigate the mechanisms underlying control of infection in hosts and offer an additional disease management strategy through selective breeding programmes [23,24,25]. For population level disease control programmes, subclinical or asymptomatic animals are an important consideration as they act as a parasitic reservoir
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