The epizootiology and control of heartwater and other tick-borne diseases of cattle in South Africa

The history of the main bovine tick-borne diseases occurring in South Africa and the role Onderstepoort played in their identification and control is briefly reviewed. The present attitudes regarding the control of tickborne diseases, taking into account their complexity, is discussed. Gaps in our knowledge regarding heartwater epizootiology and possible future studies are defined.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Studies on the ability of different strains or populations of female Rhipicephalus evertsi evertsi (Acarina: Ixodidae) to produce paralysis in sheep

Simultaneous infestation of 3-6 month-old Black-head sheep with 15 South African wild strains of Rhipicephalus evertsi evertsi males and females as well as a strain from Rwanda clearly showed that all strains are capable of inducing paralysis. Assessment of the infestation-rate of engorging female ticks during the period that their mass ranged between 15 and 21 mg/kg sheep body mass indicated that toxicity is quantitatively identical and exhibits no intraspecific gradations. The period between the beginning of infestation to the manifestation of the first clinical symptoms is, however, strain dependent: 4 days for ticks from Warmbaths, and at least 5 days for all other strains.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Proof of transovarial transmission of Cowdria ruminantium by Amblyomma hebraeum

Transovarial transmission of Cowdria ruminantium by Amblyomma hebraeum does occur in certain instances. Both the transovarial and the filial infection rates appear to be very low. The infection may reappear only in the adults or nymphae, or in all 3 stages of the tick's life cycle.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

An in vivo comparison of the efficacy of the heartwater blood and ground-up tick suspension vaccines in calves

Two groups of calves were respectively immunized with heartwater blood (BV) and ground-up tick suspension (GUTS) vaccine. A third group was left unimmunized as controls. No difference in the immune status conferred could be demonstrated between the 2 vaccines at 6 months and 12 months challenge after vaccination. An index, based on the rectal temperature before and during the reaction, was calculated as an aid in evaluating the data. In practice, the evaluation of heartwater vaccination by challenge is more effective at 12 months than at 6 months after vaccination. No effective difference was demonstrated between the 2 vaccines in their immunizing efficacy.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

In vitro cultivation of Cowdria ruminantium

Cowdria ruminantium was cultivated in a calf endothelial cell line after the cells had been irradiated at 45 & 90 GY. Another experiment in which the inoculum and non-irradiated cells were centrifuged together also yielded positive results. In some irradiated cultures, colonies of organisms could be demonstrated microscopically up to 70 days after the cultures had been inoculated with infected tick stabilate. The infectivity of cultures, even after 4 passages and 88 days post-inoculation*, was demonstrated by their intravenous injection in sheep.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Some effects of ⁶ºCo irradiation on Cowdria ruminantium in its tick host Amblyomma hebraeum Koch (Acarina: Ixodidae)

An attempt was made to attenuate Cowdria ruminantium by irradiation of the nymphal stage of its tick host, Amblyomma hebraeum. The irradiated nymphae were homogenized and serial dilutions of the resultant suspension were injected intravenously into heartwater-susceptible sheep. No attenuation could be demonstrated but the results indicate that progressively more micro-organisms will be destroyed the higher the irradiation dosage applied, and that dosages between 20 and 30 kilorad apparently prove fatal to all the pathogenic organisms.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Comparative feeding behaviour and food preferences of oxpeckers (Buphagus erythrorhynchus and B. africanus) in captivity

The feeding methods, activities and behaviour of red-billed and yellow-billed oxpeckers in captivity were compared. Both species were found to be very similar with regard to feeding. The differences observed were a greater dependance on ectoparasites such as flies and larger ticks (Amblyomma hebraeum) and a higher food intake for the yellow-billed oxpecker. These differences are the result of the larger size, limited choice of host animals and closer host/oxpecker relationship of the yellow-billed oxpecker.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Ultrastructural morphology of Cowdria ruminantium in midgut epithelial cells of adult Amblyomma hebraeum female ticks

Amblyomma hebraeum male and female ticks, experimentally infected as larvae with the Ball 3 stock of Cowdria ruminantium, were fed on a heartwater susceptible sheep. The initial attachment of the males was required as a pre-requisite for female attachment. Reticulate bodies were the predominant morphologic form of Cowdria observed in gut epithelial cells after 1-3 days of feeding. Single intermediate bodies and no elementary bodies were observed. Organisms were found within a membrane-bound vacuole and each organism had a double-unit membrane. Infrequently colonies contained homogeneous electron-dense inclusions. Groups of Cowdria organisms within a haemocyte suggested a possible dissemination of organisms from the gut to various other tissues by haemocytes.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

The efficacy of hyperimmune serum in the treatment of sweating sickness

Natural and experimental cases of sweating sickness were treated using a hyperimmune serum as specific treatment and hyperimmune serum combined with symptomatic and supportive treatment based on the clinico-pathological changes observed in cases of sweating sickness. The treatment regimens were found to be highly effective in pigs and sheep as well as in calves, although recovery in the latter species was slower.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format