Stuart J.G. Gordon

The occurrence of Culicoides species, the vectors of arboviruses, at selected trap sites in Zimbabwe

Abstract A study of the distribution of Culicoides species was conducted by establishing 12 light trap sites over five rainy seasons between 1998 and 2003 covering all the geo-climatic natural regions of Zimbabwe. In total, 279 919 specimens of Culicoides were trapped over a total of 163 trapping nights. The highest median counts of Culicoides per trapping night were recorded in natural region III, which has climatic conditions conducive to the successful development of the larvae. Culicoides imicola, the major vector of bluetongue and African horse sickness viruses in Africa, was found to be the most abundant species (80.4%), followed by Culicoides enderleini (5.9%) and Culicoides milnei (5.2%). This study identified 10 species of Culicoides that had not been previously described in Zimbabwe, including Culicoides loxodontis and Culicoides miombo, which are members of the C. imicola complex. A total of 23 994 Culicoides midges were collected from five trap sites in Harare, Zimbabwe, with the dominant species, C. imicola, representing 91.6% of the total collection. Seventeen arboviruses were isolated from these midges, 15 of which were bluetongue virus. The predominant bluetongue virus serotype was serotype 11, followed by serotypes 1, 8, 12 and 15. Bluetongue virus serotypes 1, 2, 8, 10, 12, 15, 16 and 18, detected in this study, had not been previously reported in Zimbabwe.A study of the distribution of Culicoides species was conducted by establishing 12 light trap sites over five rainy seasons between 1998 and 2003 covering all the geo-climatic natural regions of Zimbabwe. In total, 279 919 specimens of Culicoides were trapped over a total of 163 trapping nights. The highest median counts of Culicoides per trapping night were recorded in natural region III, which has climatic conditions conducive to the successful development of the larvae. Culicoides imicola, the major vector of bluetongue and African horse sickness viruses in Africa, was found to be the most abundant species (80.4%), followed by Culicoides enderleini (5.9%) and Culicoides milnei (5.2%). This study identified 10 species of Culicoides that had not been previously described in Zimbabwe, including Culicoides loxodontis and Culicoides miombo, which are members of the C. imicola complex. A total of 23 994 Culicoides midges were collected from five trap sites in Harare, Zimbabwe, with the dominant species, C. imicola, representing 91.6% of the total collection. Seventeen arboviruses were isolated from these midges, 15 of which were bluetongue virus. The predominant bluetongue virus serotype was serotype 11, followed by serotypes 1, 8, 12 and 15. Bluetongue virus serotypes 1, 2, 8, 10, 12, 15, 16 and 18, detected in this study, had not been previously reported in Zimbabwe.

The Challenges of Using Horses for Practical Teaching Purposes in Veterinary Programmes

Simple Summary Veterinary students often lack previous experience in handling horses and other large animals. This article discusses the challenges of using horses for veterinary teaching purposes and the potential consequences to student and equine welfare. The article proposes a conceptual model to optimise equine welfare, and subsequently student safety, during practical equine handling classes. Abstract Students enrolled in veterinary degrees often come from an urban background with little previous experience in handling horses and other large animals. Many veterinary degree programmes place importance on the teaching of appropriate equine handling skills, yet within the literature it is commonly reported that time allocated for practical classes often suffers due to time constraint pressure from other elements of the curriculum. The effect of this pressure on animal handling teaching time is reflected in the self-reported low level of animal handling competency, particularly equine, in students with limited prior experience with horses. This is a concern as a naive student is potentially at higher risk of injury to themselves when interacting with horses. Additionally, a naive student with limited understanding of equine behaviour may, through inconsistent or improper handling, increase the anxiety and compromise the welfare of these horses. There is a lack of literature investigating the welfare of horses in university teaching facilities, appropriate handling procedures, and student safety. This article focuses on the importance for students to be able to interpret equine behaviour and the potential consequences of poor handling skills to equine and student welfare. Lastly, the authors suggest a conceptual model to optimise equine welfare, and subsequently student safety, during practical equine handling classes.

Necrotic hepatitis associated with Clostridium novyi infection (black disease) in a horse in New Zealand

In October 2012 a 2-year-old Quarter Horse gelding was noted by the owner to be dull and listless. The animal was at pasture with one other horse on a sheep and beef station in the Hawkes Bay region of New Zealand. The owner administered oral anthelminthic to the horse using a triple-combination product containing moxidectin, praziquantel and oxfendazole. This was the first time the horse had ever been given an anthelminthic treatment. Twenty-four hours later, clinical examination by a veterinarian recorded dullness, lethargy and tachycardia. When there was no discernible improvement following the administration of a non-steroidal anti-inflammatory drug, the horse was referred to theMassey University Veterinary Teaching Hospital, Palmerston North.

Medical and surgical management of an intra-abdominal abscess of hepatic origin in a horse

CASE DESCRIPTION A 4-year-old Arabian-cross mare was examined because of a 48-hour history of pyrexia, lethargy, and signs of abdominal discomfort. CLINICAL FINDINGS On initial evaluation, the horse was in good body condition, but febrile, tachycardic, tachypneic, and icteric and had signs of colic. Findings on CBC and serum biochemical analysis indicated marked systemic inflammation and hepatocellular damage. Serial abdominal ultrasonographic examinations revealed progressive, localized hepatic parenchymal abnormalities in the left ventral aspect of the abdomen in proximity to the left liver lobes, and eventual identification of an irregularly marginated, hyperechoic walled region of heterogenous echogenicity consistent with an encapsulated hepatic abscess. TREATMENT AND OUTCOME Medical treatment was initiated with administration of doxycycline and flunixin meglumine. After 7 days, the horses clinical signs and hematologic values improved. After 14 days, the horse was discharged from the hospital and prescribed continuation of doxycycline treatment for 14 days. One week following hospital discharge, the horse was reevaluated for recurrent signs of colic and pyrexia. The horse was sedated, and the region overlying the caudal aspect of the seventh rib was desensitized with an inverted L nerve block by local infiltration with 2% lidocaine. While the horse was standing and sedated, drainage of an encapsulated intra-abdominal abscess was followed by rib resection and removal of a portion of necrotic left lateral liver lobe. The development of a pneumothorax following rib resection represented the only major surgical complication. Twelve months later, the horse was clinically normal and had returned to its previous level of performance. CLINICAL RELEVANCE Rib resection in standing sedated horses, together with appropriate medical management, should be considered an option for removal of well-encapsulated cranially located intra-abdominal abscesses that are adherent to the ventrolateral aspect of the body wall in horses.

The sero-prevalence and sero-incidence of African horse sickness and equine encephalosis in selected horse and donkey populations in Zimbabwe

Sentinel herds and samples submitted by private equine practitioners were used to determine the sero-prevalence and sero-incidence of African horse sickness virus (AHSV) and equine encephalosis virus (EEV) in horse and donkey populations in the Highveld region of Zimbabwe. The sero-prevalence and sero-incidence of antibodies against these viruses were determined using the competitive enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies. In donkeys, the median sero-prevalence of AHSV antibodies, across the three rainy seasons under study, was 75% (inter quartile range [IQR] 67–83), with a seasonal median sero-incidence of 45% (IQR 40–63). In horses, the median sero-prevalence of EEV antibodies was 63% (IQR 21–73), with a median seasonal sero-incidence of 10.5% (IQR 10–14), while in donkeys the median sero-prevalence of EEV antibodies was 80% (IQR 67–90), with a median seasonal sero-incidence of 50% (IQR 40–60). This study highlighted the significant levels of exposure of donkeys to AHSV and horses and donkeys to EEV in Zimbabwe despite equine encephalosis remaining unreported by Zimbabwean veterinarians to date. Most seroconversions in sentinel herd animals to AHSV and EEV occurred towards the end of the rainy season in March, April and May corresponding to the time of the year when the Culicoides vectors are in high abundance. In order to determine the clinical significance of these infections, blood and spleen samples, submitted by private equine veterinary practitioners over a 5-year period, from horses showing characteristic clinical signs of African horse sickness were tested for the presence of viral antigen using the antigen capture ELISA. The median sero-prevalence of AHSV antigen in horses recorded from these samples was 38% (IQR 33–88). The predominant AHSV antigen from these samples was serotype 7 (33%) followed by serotype 2 (26%) and serotypes 4 and 8 (16% each). African horse sickness virus serotypes 3 and 9, identified in this study, had not been previously reported in Zimbabwe.

A serosurvey of bluetongue and epizootic haemorrhagic disease in a convenience sample of sheep and cattle herds in Zimbabwe

A convenience sample of sheep and cattle herds around the cities of Harare, Kwekwe and Bulawayo, located in the Highveld region of Zimbabwe, was used to estimate the sero-prevalence and sero-incidence of bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) antibodies. A competitive enzyme-linked immunosorbent assay was used to identify serum antibodies against BTV and EHDV across three rainy seasons. The median sero-prevalence of BTV and EHDV antibodies in cattle was 62% (interquartile range [IQR]: 30–89) and 56% (IQR: 5–77), respectively. In sheep, the median sero-prevalence of BTV and EHDV was 41% (IQR: 19–63) and 0% (IQR: 0–21), respectively. Median sero-incidences of BTV and EHDV antibodies in cattle of 43% (IQR: 22–67) and 27% (IQR: 9–57) respectively were recorded. The median sero-incidence of BTV in sheep was 14% (IQR: 6–23). Based on these preliminary findings, animal health workers in Zimbabwe should continue to monitor the exposure rates of cattle and sheep to BTV and consider the possibility of strains emerging with increased pathogenicity. There are no previous published reports of antibodies against EHDV in Zimbabwe so the possibility of epizootic haemorrhagic disease existing in domestic livestock should now be considered by Zimbabwean animal health officials. Seroconversions to BTV and EHDV occurred predominantly at the end of each rainy season (March and April), which generally corresponds to high numbers of the Culicoides vectors. BTV isolations were made from three individual cows in two of the sentinel herds and all three were identified as serotype 3. This is the first time BTV serotype 3 has been recorded in Zimbabwe, although its presence in neighbouring South Africa is well documented.

Descriptive epidemiology of African horse sickness in Zimbabwe

A study of the prevalence of African horse sickness in horses was conducted, using records from two private equine practices in Harare for the period 1998-2004. Results indicated a higher prevalence of the disease in horses in Zimbabwe in the late rainy season (March - May). Age of the horse was found to be a significant risk factor, with foals or yearlings appearing to be 1.80 times more likely to contract the disease compared with horses older than two years. The case fatality rate in foals or yearlings was also higher than in older age groups, but this difference was not significant. The vaccination status was an important risk factor, with vaccinated horses 0.12 times less likely to die from the disease compared with unvaccinated horses. Young, unvaccinated horses therefore seem to be the most susceptible to the disease and have greater chances of fatality. This study highlights the importance of adequately protecting horses against African horse sickness by providing immunisation through vaccination and discusses the need to review current vaccination strategies being practiced in Zimbabwe.