Trypanosomosis in The Gambia: prevalence in working horses and donkeys detected by whole genome amplification and PCR, and evidence for interactions between trypanosome species.

BACKGROUND: The Gambia has an increasing population of equidae largely used for agriculture and transportation. A review of cases at The Gambian Horse and Donkey Trust (GHDT) indicated that a common reason for presentation is a poorly defined medical condition often attributed to trypanosomosis. There are few reports describing the prevalence or the range of clinical signs associated with infection with different species of trypanosomes in horses and donkeys, but given the importance of these animals, the role of trypanosomosis requires investigation. RESULTS: In total 241 animals from the Central River Division in The Gambia (183 horses and 58 donkeys) were screened using Whole Genome Amplification (WGA) followed by trypanosome species identification using polymerase chain reaction (PCR). The results indicated overall trypanosome prevalence of 91%; with an infection rate of 31% for Trypanosoma congolense Savannah, 87% for Trypanosoma vivax and 18% for Trypanosoma brucei sp. Multiple species were present in 43% of infections. Microscopy had a good specificity (100%) and positive predictive value (100%) for trypanosome detection, but the sensitivity (20%) and negative predictive value (10.5%) were low relative to PCR-based diagnosis. Infection with T congolense showed the greatest negative effect on packed cell volume (PCV), while infection with T. brucei sp also had a significant, although lesser, negative effect on PCV. In addition, cases positive by microscopy were associated with significantly lower PCV. However, concurrent infection with T. vivax appeared to cause less effect on PCV, compared to animals infected with T. congolense alone. CONCLUSION: The prevalence of Trypanosomosis was high in both horses and donkeys. Infection with T. congolense appeared to have the greatest clinical significance, while T. vivax infection may be of limited clinical significance in this population. Indeed, there is evidence of T. vivax co-infection ameliorating the pathology caused by T. congolense. WGA and PCR allowed a more comprehensive analysis of field infections with the detection of infections below the threshold of microscopy, and provided indications of interactions between parasite species that would otherwise remain undetected. The study raises important questions about the epidemiology of trypanosome infection in relation to disease that require a full scale longitudinal analysis.

The effect of inotropic and/or vasopressor support on postoperative survival following equine colic surgery.

OBJECTIVE: To determine the effects of dobutamine and phenylephrine on intra- and postoperative survival in horses undergoing emergency abdominal surgery. STUDY DESIGN: Retrospective case analysis. ANIMALS: A total of 637 client-owned horses undergoing colic surgery. METHODS: Clinical details of horses admitted for colic surgery were recorded on a computer database. Information collected included history, clinical variables observed before surgery, anaesthesia and surgical details, and postoperative survival and morbidity rates. Details of specific importance for this study were those recorded during anaesthesia, in particular the duration of dobutamine and phenylephrine administration, separately and combined, and total anaesthesia time. Two outcomes were considered: 1) intra-operative death, i.e. death between time of pre-anaesthetic medication and recovery from anaesthesia (defined as horse walking from recovery box); and 2) all deaths, i.e. death at any time after induction of anaesthesia. The definition of 'death' included euthanasia. Univariable and multivariable statistical analyses were performed to evaluate the associations between dobutamine and/or phenylephrine use and these two outcomes. RESULTS: Results from univariable analyses suggested that dobutamine administration was not significantly associated with increased intra- or postoperative mortality. Phenylephrine administration showed univariable association with intra- and postoperative death. However, in multivariable models adjusted for the effects of heart rate and packed cell volume at admission, the phenylephrine effect was not significantly associated with intra-operative, or other types of death. CONCLUSION: This study provides no evidence to suggest that dobutamine or phenylephrine administration is associated with altered survival rates during or after colic surgery. CLINICAL RELEVANCE: Our study supports previous work, suggesting that pre-existing cardiovascular status is an important prognostic determinant in equine colic cases. It provides no evidence that dobutamine or phenylephrine administration is associated with survival.