Parasites of domestic and wild animals in South Africa. XXXVIII. Ixodid ticks collected from 23 wild carnivore species

Ixodid ticks were collected from 104 wild carnivores belonging to 23 species in various nature reserves and on several farms in all nine provinces of South Africa. Seven feral cats in a nature reserve were also examined. Twenty-four tick species belonging to seven genera were recovered and identified. Amongst these ticks we consider the adults of Haemaphysalis leachi, Haemaphysalis spinulosa, Haemaphysalis zumpti, Ixodes rubicundus, Rhipicentor nuttalli, Rhipicephalus simus and Rhipicephalus turanicus to be true parasites of wild carnivores. Although numerous adult Rhipicephalus appendiculatus and Rhipicephalus zambeziensis were collected from some lions these were either sick or old animals. The immature stages of seven species regularly utilized wild carnivores as hosts on an opportunistic basis.     

Potential Inoculum Sources of Phaeomoniella chlamydospora in South African Grapevine Nurseries

Petri disease of grapevine is primarily caused by Phaeomoniella chlamydospora. This pathogen affects mostly young grapevines, but is also implicated in esca disease of older grapevines. Little is known about the disease cycle of this fungus. Infected propagation material was identified as a major means of dissemination of the pathogen. Recently, the pathogen was also detected from soil in South Africa and airborne conidia have been found in vineyards. The aim of this study was to use a molecular detection technique to test different samples collected from nurseries in South Africa at different nursery stages for the presence of P. chlamydospora. A one-tube nested-PCR technique was optimised for detecting P. chlamydospora in DNA extracted from soil, water, callusing medium and grapevine wood. The one-tube nested-PCR was sensitive enough to detect as little as 1 fg of P. chlamydospora genomic DNA from water and 10 fg from wood, callusing medium and soil. PCR analyses of the different nursery samples revealed the presence of several putative 360 bp P. chlamydospora specific bands. Subsequent sequence analyses and/or restriction enzyme digestions of all 360 bp PCR bands confirmed that all bands were P. chlamydospora specific, except for five bands obtained from callusing media and one from water. Phaeomoniella chlamydospora was positively detected in 25% of rootstock cane sections collected from mother blocks, 42% of rootstock cuttings and 16% of scion cuttings collected during grafting, 40% of water samples collected after pre-storage hydration, 67% of water samples collected during grafting, 8% of callusing medium samples and 17% of soil samples collected from mother blocks. These media can therefore be considered as possible inoculum sources of the pathogen during the nursery stages.     

A target-site mutation is present in a glyphosate-resistant Lolium rigidum population

Annual ryegrass (Lolium rigidum) is the only weed species to have evolved resistance to the broad‐spectrum herbicide glyphosate in Australia. A population that had failed to be controlled by glyphosate was collected from a vineyard in the Adelaide Hills region of South Australia. Dose–response experiments on this population (SLR 77) showed that it was glyphosate resistant, with an LD₅₀ that was 1.9–3.4 times higher than that of a susceptible population (VLR 1). The movement of radiolabelled glyphosate within SLR 77 plants showed that this population did not have the differential glyphosate translocation mechanism of resistance common to several other Australian glyphosate‐resistant populations. Subsequent analysis of shikimic acid accumulation within the plant after glyphosate treatment showed that this population accumulated significantly less shikimic acid than a susceptible population, but more than a glyphosate‐resistant population with the translocation mechanism, indicating the possible involvement of another mechanism of resistance. Sequencing of a portion of the SLR 77 5‐enolpyruvylshikimate‐3‐phosphate synthase gene was carried out and a mutation causing an amino acid change at position 106 from proline to threonine was identified. This mutation is likely to be responsible for glyphosate resistance in this population, as mutations in this position have been found to be responsible for glyphosate resistance in goosegrass (Eleusine indica) from Malaysia. This paper represents the first report of target‐site glyphosate resistance in L. rigidum and provides evidence that this species has at least two mechanisms of glyphosate resistance present in Australia.     

Control of black foot disease in grapevine nurseries

Black foot disease of grapevines is a decline and dieback disease caused by a soilborne pathogen complex including Cylindrocarpon liriodendri , C. macrodidymum , Campylocarpon fasciculare and Campyl. pseudofasciculare . These pathogens cause primary infections of roots and basal ends of grafted cuttings in nursery soils. Thirteen fungicides were screened in vitro for mycelial inhibition of these pathogens. Prochloraz manganese chloride, benomyl, flusilazole and imazalil were the most effective fungicides tested, and were subsequently included in semi-commercial field trials. Basal ends of grafted cuttings were dipped in various chemical and biological treatments prior to planting in open-rooted nurseries. Black foot pathogens were not isolated from grafted cuttings prior to planting. Additional treatments involved soil amendments with Trichoderma formulations and hot water treatment of dormant nursery grapevines. Field trials were evaluated after eight months. Isolations from uprooted plants revealed low levels of black foot pathogens in the roots of untreated control plants, and significantly higher levels in basal ends of rootstocks. The incidence of black foot pathogens, as well as that of Petri disease pathogens, was not significantly and/or consistently reduced by the majority of chemical or biological treatments. However, these pathogens were not isolated from uprooted plants that were subjected to hot water treatment. It is therefore recommended that hot water treatment of dormant nursery plants be included in an integrated strategy for the proactive management of these diseases in grapevine nurseries.     

Bluetongue virus serotypes 1 and 3 infection in Poll Dorset sheep

Objective To study the clinical signs following bluetongue virus serotypes 1 and 3 infection in Poll Dorset sheep.
Design A clinical and pathological study.
Procedure Twenty Poll Dorset sheep were inoculated with bluetongue virus serotypes 1 or 3, each inoculum having a different passage history. The sheep were examined daily and their clinical appearance and rectal temperatures recorded. Heparinised and non-heparinised blood samples were taken at intervals for virological and serological study. Gross pathological findings were recorded for several sheep at necropsy and tissue samples were collected from three sheep for virological studies.
Results All inoculated sheep developed clinical disease. The clinical signs and gross pathological changes varied considerably but were consistent with damage to the vascular endothelial system. There was a decline in the titres of infectious bluetongue virus and of antigen in tissues collected between 7 and 12 days after infection.
Conclusions The severity of disease was related to the speed of onset and duration of pyrexia and not the development or titre of viraemia. Generally, those animals with sensitive mouths, depression, coronitis, recumbency and reluctance to move were the most debilitated. Whole blood was the most reliable source of infectious virus from acutely and chronically infected and convalescent animals. However, tissue samples particularly spleen, collected from dead or killed animals suffering from either peracute or acute forms of disease were most appropriate for the rapid confirmation of a clinical diagnosis.     

The efficacy of used engine oil against ticks on cattle

The study was conducted in a peri-urban agricultural system at Botshabelo, a city in the south-eastern Free State. A questionnaire survey revealed that 88.5% of cattle farmers in the area experienced problems related to ticks and tick-borne diseases. Because of the cost of commercial acaricides the Botshabelo farmers use alternative, cheaper methods of tick control, including the application of used engine oil. The specific aim of the study was to determine whether used engine oil can effectively control ticks on cattle. From March to August 1996 the tick burdens of ten control animals and six animals treated by their owner with used engine oil were compared. The total tick burdens for the 6 month period differed significantly between the two experimental groups. The efficacy of the used engine oil on the treated group varied between 15.1% and 64.8% with a mean of 38.1%. Although commercial acaricides can be more cost-effective, the application of used engine oil can be useful to reduce tick numbers on cattle during periods of peak abundance. Another advantage in that the use of the oil will not influence existing endemic stability of Anaplasma marginale and Babesia bigemina infections because of the residual tick burdens after treatment.     

Tick diversity, abundance and seasonal dynamics in a resource-poor urban environment in the Free State Province

The objectives of this study were to determine the diversity, seasonal dynamics and abundance of ticks infesting cattle in urban, small-scale farming communities in and around Botshabelo and Thaba Nchu in the eastern Free State Province, South Africa. A total of ten cattle, ear-tagged for individual identification, were investigated monthly at each of five localities. Adult ticks were removed from the right hand side of each animal and placed in containers filled with 70% ethanol. They were subsequently identified and their numbers quantified. Immature Otobius megnini were counted but not removed. A total of 244,538 adult ticks of ten different species were collected over the 12-month study period. The tick species, in decreasing order of relative abundance, were: Boophilus decoloratus (87.26%), Rhipicephalus evertsi evertsi (6.86%), Hyalomma marginatum rufipes (2.42%), Otobius megnini (1.85%) Rhipicephalus follis (0.76%), Rhipicephalus gertrudae (0.54%), Rhipicephalus sp. (0.21%), Ixodes rubicundus (0.08%), Hyalomma truncatum (0.01%) and Margaropus winthemi (0.004%). The three most abundant species, namely B. decoloratus, R. evertsi evertsi and H. marginatum rufipes, occurred at all localities but with significant differences in abundance. M. winthemi ticks occurred only in the Thaba Nchu area and were not found at any of the there localities in Botshabelo. Significant differences in tick burdens between the six warm months (September to February) and the six cooler months (March to August) were found for most of the species recorded. Boophilus decoloratus occurred in significantly higher numbers in autumn (March to May) and winter (June to August) compared to spring (September to November) and summer (December to February), with 76.8% of the total B. decoloratus burden occurring during the cooler months.     

Effect of the route of administration on the mucosal and systemic immune responses to Lawsonia intracellularis vaccine in pigs

In an on‐farm study, 40 weaned piglets aged 3 weeks were vaccinated with Lawsonia intracellularis vaccine orally, IM or IP while a fourth group remained unvaccinated. All vaccinated animals showed increased serum levels of L. intracellularis‐specific IgG antibodies, but significantly elevated concentrations of specific IgG, IgA and cytokines were generated in ileal mucosal secretions from the orally and IP vaccinated pigs when examined at 17 days after vaccination.     

New method using quantitative PCR to follow the tick blood meal and to assess the anti-feeding effect of topical acaricide against Rhipicephalus sanguineus on dogs

A 28-day study was conducted to assess the dynamic of blood feeding by Rhipicephalus sanguineus ticks on dogs treated or not with a novel topical combination of fipronil, amitraz and (S)-methoprene. Dogs were infested weekly through exposure to ticks in crates for 4 h. Ticks were then counted in the crates at 2 h and 4 h post dog exposure. Ticks were also counted and removed from the dogs at 2 h, 4 h, 6 h, 12 h and 24 h post tick exposure. The inhibition of blood feeding was assessed by both tick quantification and designing and performing a quantitative PCR (qPCR) to detect the canine hydroxymethylbilane synthase (HMBS) gene in ticks. The percentage of repellency sensu lato based on the ticks collected in crates at 2 h varied from 4.7% at day 28 to 48.3% at day 7. The immediate mortality rate of the ticks expelled at 2 h varied from 1.5% at day 21 to 31.7% at day 7. The efficacy calculation showed that the acaricidal combination started to kill ticks in as little as 2 h. The average efficacy reached 90.0% at 12 h post crate challenges and 100% at 24 h post exposure in crates. The inclusion of an internal amplification control was used to ensure that no significant template-derived PCR inhibition (≤6.2%) affected the overall results. The reduction of blood feeding was significant at 4 h (>80.0%) and >99.0% at 24 h post tick exposure in the crate. The high repellency rate and the lethal efficacy of CERTIFECT^® resulted in significantly fewer live attached ticks, consequently reducing blood intake and fluid exchanges.     

Effect of Leptin on In Vivo Goat Embryo Production

The aim of this study was to evaluate the effect of leptin administration during superovulation on in vivo goat embryo production. Ten mature does were superovulated with 133 mg follicle‐stimulating hormone (FSH) i.m. in six descending doses at 12‐h intervals. The goats received 4.8 μg/kg human recombinant leptin s.c. (leptin group, n = 5) or phosphate‐buffered saline (PBS) (control group, n = 5) with the first and second FSH doses. The does were mated and subjected to embryo collection by transcervical technique 6 days later. The total number of cells per embryo and the number of cells with fragmented DNA were assessed in selected blastocysts by combining Hoechst 33342 and terminal dUTP nick‐end labelling (TUNEL) staining. Plasma concentrations of oestradiol (E₂) and progesterone (P₄) were determined by electrochemiluminescence from the day of FSH treatment, on the day of superovulatory oestrus and on the day before embryo collection. Compared with the control group, the does that received leptin had a higher number of transferable embryos (p < 0.005), fewer embryos classified as degenerated (p < 0.001) and fewer TUNEL‐positive cells/blastocyst (p < 0.001). The number of transferable embryos was positively correlated with E₂ concentrations on day of oestrus (r = 0.562; p < 0.01) and P₄ concentrations on the day of embryo collection (r = 0.912; p < 0.001). We concluded that in vivo leptin administration during FSH treatment improved embryo quality and affected ovarian steroidogenesis in superovulated goats.