Journal of the South African Veterinary Association

Rumen management during aphagia

Ruminants that for any reason are unable to eat enough to survive can be supported via rumen fistulation. To successfully accomplish this task, an understanding of rumen physiology is necessary. Some adaptation and modification of the normal physiological processes will be necessary because the extended time normally required to ingest food will, for obvious practical reasons, be reduced to a few minutes repeated once to three times a day. The physiology of significance to aphagic or dysphagic animals is discussed and relevant examples of clinical cases are used to illustrate practical applications.

The use of the milk ring test and rose bengal test in brucellosis control and eradication in Nigeria

In this study, milk and blood samples collected simultaneously from 532 trade cows to be slaughtered at Bodija abattoir, Ibadan (southwestern, Nigeria) were examined for antibodies to Brucella using the milk ring test (MRT) and the rose bengal test (RBT). Overall, 18.61 % of the milk samples were positive according to the MRT, while 9.77 % of the serum samples were positive according to the RBT. The difference was highly significant (Chi-square value 16.33; P < 0.05); only 32 (6.02 %) of the samples were positive for both tests. The Red Bororo breed of cattle and the White Fulani had the highest positive rates, namely 20.93 % and 11.69 % for the MRT and RBT respectively. No conclusion can be drawn about sensitivity because we do not know the true status of the animals tested. It is, however, obvious that although the MRT and RBT are 1st-line screening tests for brucellosis in cows in some countries, their lack of specificity is of concern. Therefore, the requirement for other confirmatory tests that are more specific should be considered for control and eradication of the disease, especially in Nigeria.

Ixodid ticks infesting domestic goats in communal land areas of Zimbabwe

The purpose of this study was to determine the species spectrum of ticks infesting goats owned by resource-limited farmers in the state-owned communal land areas of Zimbabwe. Ticks were collected from goats at a single locality within each of 5 communal land areas, and a total of 14 ixodid tick species was recovered. The most numerous tick was Rhipicephalus evertsi evertsi, which was present in all areas at each sampling, and a Rhipicephalus sp. (near R. punctatus), which was most abundant on goats in the central regions of Zimbabwe during the March rainy season. Amblyomma hebraeum was present on goats in all areas sampled. In the eastern central region its distribution overlapped that of Amblyomma variegatum, while in the northwest it overlapped those of both Amblyomma marmoreum and A. variegatum. Hyalomma truncatum was present at all localities, whereas only a single Hyalomma rufipes was recovered. Rhipicephalus appendiculatus was collected from goats in the moist, slightly cooler regions, while the few Rhipicephalus zambeziensis recovered were present in the hotter, drier regions. Species recorded in lower numbers were Rhipicephalus (Boophilus) decoloratus, Rhipicephalus lunulatus, Rhipicephalus simus, Rhipicephalus tricuspis and Rhipicephalus turanicus. Attachment in the inter-digital space of adult A. hebreaum and H. truncatum was sometimes associated with lameness.

**Thermal, cardiorespiratory and cortisol responses of impala (Aepyceros melampus) to chemical immobilisation with 4 different drug combinations**

Thermometric data loggers were surgically implanted in 15 impala (Aepyceros melampus)to investigate the consequences of chemical capture. Impala were darted and chemically immobilised for 30 min with each of the following drug combinations: etorphine and azaperone; etorphine and medetomidine; thiafentanil and azaperone, and a thiafentanil medetomidine combination. During immobilisation, pulse oximeter readings, respiratory rhythm, the plane of immobilisation and plasma cortisol concentrations were measured and recorded. The impala developed an extremely high rise in body temperature, which peaked 20-30 min after reversal of the immobilisation. The magnitude of the rise in body temperature was similar for all the drug combinations (F = 0.8, P = 0.5), but the duration of the hyperthermia was shorter when the thiafentanil and azaperone combination was used (F = 3.35, P < 0.05). Changes in body temperature were related to the time that it tookfor an animal to become recumbent after darting (r² = 0.45, P = 0.006) and not to the effect of the drug combination on time to recumbency (r² = 0.29, P = 0.46). The relationship between time to recumbency and body temperature change, and also to plasma cortisol concentration (r² = 0.67, P = 0.008), indicated that physiological consequences of capture were related to the duration of exposure to a stressor, and not to the pharmacology of the capture drugs. Although shorter time to recumbency in individuals resulted in the benefit of smaller stress responses and body temperature changes, those individuals were predisposed to developing hypoxia and possibly induction apnoea. When animals are chemically immobilised, reducing the thermal consequences of capture requires limiting the exposure of the animal to a psychological 'fright stress'.

The extent of acaricide resistance in 1-, 2- and 3-host ticks on communally grazed cattle in the eastern region of the Eastern Cape Province, South Africa

In order to determine the extent of acaricide resistance in the eastern region of the Eastern Cape Province 1-, 2- and 3-host ticks were collected from cattle at 59 dip-tanks over a period of 2 years. These ticks were tested for resistance against 3 compounds, namely amitraz, cypermethrin and chlorfenvinphos. The Shaw Larval Immersion Test detected emerging resistance to amitraz in Rhipicephalus (Boophilus) microplus at 2 dip-tanks and resistance at a 3rd. It also revealed resistance in this tick to cypermethrin at 1 dip-tank and emerging resistance to chlorfen vinphos at 8 dip-tanks and resistance at 2. Rhipicephalus evertsi evertsi was susceptible to amitraz and cypermethrin at all dip-tanks, but showed emerging resistance to chlorfenvinphos at 7 dip-tanks and resistance at 4. Rhipicephalus appendiculatus was susceptible to amitraz and chlorfenvinphos at all dip-tanks and demonstrated emerging resistance to cypermethrin at 1. With the exception of R. (B.) microplus, in which emerging resistance to amitraz was detected at 1 dip-tank by the Reproductive Estimate Test, all 3 tick species at all dip-tanks at which sufficient numbers of ticks had been collected were susceptible to the 3 acaracides in both the Egg Laying Test and the Reproductive Estimate Test. The localities at which acaricide resistance was recorded were mapped.

**Gammaherpesvirus carrier status of black wildebeest (Connochaetes gnou) in South Africa**

Malignant catarrhal fever (MCF) is an economically important disease primarily of domestic cattle with a high case fatality rate. It is causedby either alcelaphine herpesvirus type 1 (AlHV-1) or ovine herpesvirus type 2 (OvHV-2). The major reservoir host of AlHV-1 is the blue wildebeest (Connochaetes taurinus),but it is generally accepted that the black wildebeest (Connochaetes gnou) is also a reservoir host. No viral studies in the black wildebeest have been reported and the carrier status of black wildebeest has not been documented. Specimens were collected from several game farms and conservation areas in central South Africa representing the geographical area historically linked to the natural habitat of the black wildebeest. Specimens were obtained from 304 black wildebeest of different ages and sex, as well as 51 black wildebeest foetuses at different stages of gestation. Virus was isolated from a black wildebeest calf. Morphological features and antigenic characteristics suggested it to be a gammaherpesvirus closely related to AlHV-1. All serum samples tested positive with a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) for group-specific malignant catarrhal fever virus antibody. A SYBR Green real-time PCR assay was developed for the detection of gammaherpesviral DNA. Only 15.8 % of the animals tested positive with the real-time PCR assay whereas 90 % of the foetuses tested positive. This finding suggests that, unlike OvHV-2 infection in lambs in which the infection takes place after weaning, the virus in black wildebeest is mainly transmitted in utero or soon after birth. The results suggest that black wildebeest are latent carriers of a gammaherpesvirus similar or closely related to AlHV-1 present in blue wildebeest and that it is likely that all black wildebeest are persistently infected.

Sex-based comparison of limb segmentation in ostriches aged 14 months with and without tibiotarsal rotation

The aim of this study was to propose equations to predict changes that occur over time in the angular position of the bones during motion and the angular velocity of the bones in forward motion as a consequence of tibiotarsal rotation (TTR) in ostriches aged 14 months. Twenty-four normal 14-month-old ostriches (12 cocks and 12 hens) and 20 birds with TTR (9 cocks and 11 hens) were used in the study. Daily readings of temperature, relative humidity and rainfall, the lengths of the different segments of the legs and wings, the perpendicular height from the top of the torso to ground level and the length of the erect neck were recorded. Measurements of the degree of valgus deformity in the left foot were made where applicable. TTR hens and cocks were smaller in stature than normal birds. Comparing TTR hens and cocks, the toe, claw, humerus, perpendicular height and angle of rotation were larger in cocks, indicating a larger body in cocks. Hens were more severely affected by TTR. We suggest that the equations used in this study will assist in measuring movement of ostriches and how movement is compromised by overcrowding and TTR. Birds suffering from TTR may experience an increased degree of stress due to movement restrictions in confinement.

Limb fracture during recovery from general anaesthesia: An often tragic complication of equine anaesthesia

A 10-year-old Thoroughbred mare was presented for lameness of the left hindlimb as a result of an apical fracture of the lateral proximal sesamoid bone. The mare was ultimately euthanased after suffering catastrophic fractures of the 3rd and 4th metatarsal bones of the contra-lateral hindlimb during an uncoordinated attempt to rise during recovery from general anaesthesia after undergoing arthroscopic surgery. The case report focuses mostly on horse anaesthesia-related mortality, anaesthetic procedure in the horse, possible causes of fractures in horses during recovery and ways in which rate of occurrence of these fractures can be minimised.

An outbreak of toxoplasmosis in an aviary collection of Nicobar pigeons (Caloenas nicobaria)

Three out of 10 Nicobar pigeons (Caloenas nicobaria) in an aviary collection in South Africa were found dead with no presenting clinical symptoms. Histological examination of formalin-fixed tissues from all these birds revealed necrotic foci in various visceral organs (liver, spleen, heart, kidney and lungs), plus diffuse pulmonary congestion and oedema with vasculitis. Numerous protozoal tachyzoites were present in all organs and there was strong positive immunohistochemical (IHC) labelling of these organisms for Toxoplasma gondii. Pathology was consistent with acute systemic toxoplasmosis as a consequence of oocyst ingestion. Feral cats were known to be a problem at the facility. Clinical toxoplasmosis is rarely reported in pigeons and this is believed to be the 1st report of toxoplasmosis in Nicobar pigeons.

Lack of correlation between the electrical conductivity of milk and the blood progesterone levels in cows

A study was conducted to investigate the possibility of measuring the electrical conductivity (EC) of cow's milk as a practical and cost-effective means of determining oestrus in cows. Prostaglandin injections were used to synchronise the oestrous cycle of 15 cows. From the onset of oestrus, milk and blood samples were collected from each cow every 2nd day over a period of 22 days. A portable, commercially available instrument was used to measure the EC of the milk. The blood progesterone levels were determined by means of an enzyme immuno-assay method. No correlation was found between the EC of milk and the blood progesterone levels of the cows tested. Electrical conductivity measurements of milk are of no value in determining the onset of oestrus in cows.