Scielo RSS <![CDATA[Onderstepoort Journal of Veterinary Research]]> vol. 75 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Molecular characterization of SAT-2 foot-and-mouth disease virus isolates obtained from cattle during a four-month period in 2001 in Limpopo Province, South Africa</b>]]> Foot-and-mouth disease (FMD) is an acute, highly contagious viral infection of domestic and wild cloven-hoofed animals. The virus is a single-stranded RNA virus that has a high rate of nucleotide mutation and amino acid substitution. In southern Africa the South African Territories (SAT) 1-3 serotypes of FMD virus are maintained by large numbers of African buffaloes (Syncerus caffer), which provide a potential source of infection for domestic livestock and wild animals. During February 2001, an outbreak of SAT-2 was recorded in cattle in the FMD control zone of South Africa, adjacent to the Kruger National Park (KNP). They had not been vaccinated against the disease since they form the buffer between the vaccination and free zones but in the face of the outbreak, they were vaccinated as part of the control measures to contain the disease. The virus was, however, isolated from some of them on several occasions up to May 2001. These isolates were characterized to determine the rate of genetic change in the main antigenic determinant, the 1D/2A gene. Nucleotide substitutions at 12 different sites were identified of which five led to amino acid changes. Three of these occurred in known antigenic sites, viz. the GH-loop and C-terminal part of the protein, and two of these have previously been shown to be subject to positive selection. Likelihood models indicated that the ratio of non-synonymous to synonymous changes among the outbreak sequences recovered from cattle was four times higher than among comparable sequences isolated from wildlife, suggesting that the virus may be under greater selective pressure during rapid transmission events. <![CDATA[<b>Value of tests for evaluating udder health in dairy goats: Somatic cell counts, California Milk Cell Test and electrical conductivity</b>]]> The value of electric conductivity (EC), California Milk Cell Test (CMCT) and somatic cell count (SCC) as diagnostic tools was investigated in dairy goats. Conductivity colour reading correlated with SCC. Milk samples with conductivity colour red had significantly higher SCC than those with conductivity colours green and orange (P < 0.001). There were moderate positive correlations between CMCT (R² = 0.470), and conductivity score and CMCT and conductivity colour readings (R² = 0.597). Conductivity scores were significantly (P < 0.001) higher during and after intra-mammary treatment with Cloxamast LC and conductivity colours were significantly different between treatment and control groups (P < 0.001). There was a weak positive correlation between conductivity colour and stage of lactation (R² = 0.317) and a moderately positive correlation between conductivity score and stage of lactation (R² = 0.523). A moderately negative correlation was shown between milk yield and conductivity score (R² = -0.426) and between milk yield and conductivity colour (R² = -0.433). Moderate positive correlations were present between CMCT and SCC (R² = 0.689) and between CMCT and stage of lactation (R² = 0.459). CMCT ratings were significantly different (P < 0.001) for the intra-mammary treatment groups. CMCT ratings for infected and non-infected udder halves (P = 0.008) were significantly different; as were those for infected and non-infected udder halves and for left and right udder halves separately (P = 0.010). CMCT ratings for milk samples with SCC above and below 750 x 10³ cells per ml were significantly different (P < 0.001) as well as for milk from treated and control udder halves with SCC below or above 750 x 10³ cells per ml(P < 0.001). CMCT was found to be more accurate for indicating the absence of mastitis than for diagnosing it. There were significant differences in log SCC between treatment and control groups, during and after treatment. Infected udder halves had significantly higher log SCC than non-infected udder halves before and after treatment, but not during treatment. There was a moderate positive correlation between stage of lactation and SCC (R² = 0.438). <![CDATA[<b>Macroscopic features of the venous drainage of the reproductive system of the male ostrich (<i>Struthio camelus</i>)</b>]]> The macroscopic features of the venous drainage of the reproductive system of the male ostrich were studied in six pre-pubertal and three sexually mature and active birds. Each testis was drained by one to four testicular veins. The right testicular veins drained the right testis and epididymis and its appendix to the caudal vena cava and to the right common iliac vein, whereas the left testicular veins drained the left testis and epididymis and its appendix exclusively to the left common iliac vein. A number of variations in the drainage pattern based on the point of entry and number of testicular veins were observed. The cranial aspect of the testis was also linked to the caudal vena cava or common iliac vein via the adrenal veins. The cranial, middle and caudal segments of the ductus deferens (and ureter) were drained by the cranial, middle and caudal ureterodeferential veins respectively, to the caudal testicular veins, the caudal renal veins and pudendal/caudal part of the internal iliac veins. In some specimens, the caudal ureterodeferential veins also drained into the caudal mesenteric vein. The surface of the phallus was drained by tributaries of the pudendal vein. The basic pattern of venous drainage of the reproductive organs of the male ostrich was generally similar to that described for the domestic fowl. However, important differences, including the partial fusion of the caudal renal veins, drainage of the cranial aspect of the testes via the adrenal veins, drainage of the caudal ureterodeferential veins into the caudal mesenteric vein and the presence of veins draining the surface of the phallus, were observed. Although significant, these differences may simply reflect variations in the normal pattern of venous drainage of the reproductive tract of birds which could be verified by studying more specimens and more species. <![CDATA[<b>Evaluation of larvicides in developing management guidelines for long-term control of pest blackflies (Diptera: Simuliidae) along the Orange River, South Africa</b>]]> In 2000 and 2001 Orange River levels were higher than normal: associated serious outbreaks of blackfly had a substantial detrimental impact on the local economy. The poor control was attributed to the suspected development of larval resistance to temephos. A long-term solution to blackfly control, through the identification of a suitable replacement to temephos for use during high flow conditions, was proposed. This study, however, failed to identify or register a suitable larvicide for use during high flow conditions. Although permethrin was highly effective against blackfly larvae, it was rejected because of its detrimental impacts on non-target fauna. Various formulations of locally produced dry Bacillus thuringiensis var. israelensis (B.t.i.) were tested, but these were ineffective against blackflies. The study also confirmed that resistance to temephos has developed among Simulium chutteri in the middle and lower Orange River. The feasibility of "reversing" the resistance to temephos through the use of the synergist piperonyl butoxide (PEO) was investigated, but the results were not favourable. Furthermore, PBO was highly toxic to blackflies and non-target organisms, and was not recommended for further testing. This means that B.t.i. currently remains the only symptomatic measure of treatment currently applied. Although resistance to B.t.i. has not been reported for blackflies elsewhere in South Africa, there is a need to remain vigilant and to implement an operational strategy that minimizes the risks of resistance developing. <![CDATA[<b>Prevalence of the dog nematode <i>Spirocerca lupi </i>in populations of its intermediate dung beetle host in the Tshwane (Pretoria) Metropole, South Africa</b>]]> Spirocerca lupi (Spirurida: Spirocercidae) is a cosmopolitan parasite, principally of domestic dogs and dung beetles are its main intermediate hosts. In South Africa there has recently been growing concern over the upsurge of reported cases of clinical spirocercosis in dogs, while little is known or understood about the dynamics of the host-parasite associations between dung beetles and this nematode. We determined and compared the prevalence of infection in dung beetles between rural, urban and periurban areas of Tshwane (Pretoria) Metropole. Dung beetles were sampled during April and October 2006, at various localities in each of these areas. Localities were selected on the basis of being focal areas of high infection with S. lupi in dogs. Pig, dog and cow dung-baited pitfall traps were used for sampling the beetles. Trap contents were collected 48 h after the traps had been set and only dung beetles were collected from the traps. In total, 453 specimens belonging to 18 species were collected from 63 pitfall traps in all three areas. The numbers of species that were collected varied among the three areas. Dung beetles, irrespective of species (18) and numbers (447), predominantly preferred pig dung. The prevalence of dung beetles infected with the larvae of S. lupi varied considerably in the three areas. In the urban area 13.5 % of the dung beetles dissected were infected, while the prevalence of S. lupi in dung beetles in the rural area was 2.3 %. All the dung beetles that were infected with this nematode showed a preference for omnivore (pig and dog) dung. <![CDATA[<b>Pentastomid parasites in fish in the Olifants and Incomati River systems, South Africa</b>]]> During parasitological field surveys of freshwater fish, sebekiid and subtriquetrid pentastome larvae were recovered from the body cavity or swim bladder of several fish species from various localities in Limpopo and Mpumalanga Provinces, South Africa. Sebekia wedliwas recovered from the body cavity of Marcusenius macrolepidotus (Mormyridae) from Flag Boshielo Dam, Limpopo Province, and Alofia sp. and Subtriquetra rileyi were found in the swim bladder of Oreochromis mossambicus (Cichlidae) from the Phalaborwa Barrage, Limpopo Province. The latter species was also collected from the swim bladder of O. mossambicus in dams in the Phalaborwa region and the Ga-Selati River, Limpopo Province. A single specimen of Sebekia okavangoensis was present in the body cavity of Clarias gariepinus (Clariidae) in a dam on a sugarcane farm in the Komatipoort region, Mpumalanga Province. Pentastomid infections in the Mormyridae and Clariidae represent new host records. <![CDATA[<b>Production trials involving use of the FAMACHA© system for haemonchosis in sheep: Preliminary results</b>]]> In three trials conducted on two separate farms the production of sheep treated for naturally acquired haemonchosis using the FAMACHA© system of targeted selective treatment (TST) (i.e. to treat only those animals unable to manage unaided in the face of heavy Haemonchus challenge) was compared to that of suppressively drenched sheep in the same flock. As expected by the research team who developed and evaluated the FAMACHA© system, TST did result in some loss in production. However, despite high levels of worm challenge in two of the trials and the fact that the comparison was with suppressive drenching which is not sustainable, the total effect was relatively small in relation to the important advantage of using the TST as regards reduced selection for anthelmintic resistance (AR). Concerning the sustainability of worm control, it is concluded that the development of drug resistance to anthelmintics leaves sheep and goat farmers in South Africa no choice but to use methods of TST such as FAMACHA©. The FAMACHA© system can also be a useful clinical aid for early on-farm detection of AR by farmers; the degree of improvement in the colour of the ocular mucous membrane from pale to red in individually drenched anaemic animals over a period of 7-14 days can give a good indication of the efficacy of the compound(s) used. <![CDATA[<b>A rapid and sensitive real-time reverse transcription PCR for the pathotyping of South African H5N2 avian influenza viruses</b>]]> A Fluorescence resonance energy transfer (FRET) real-time reverse-transcription (rRT-PCR) assay was developed that distinguishes stains of South African and European highly pathogenic (HPAI) from low pathogenicity (LPAI) H5 avian influenza viruses in the absence of virus isolation, irrespective of the length of insertion at the hemagglutinin cleavage site (H0). The assay was used to pathotype H5-type viruses detected by rRT-PCR in ostrich tracheal swabs collected during the 2006 HPAI H5N2 outbreak in the Western Cape Province. <![CDATA[<b>Sequence and phylogenetic analysis of chicken anaemia virus obtained from backyard and commercial chickens in Nigeria</b>]]> This work reports the first molecular analysis study of chicken anaemia virus (CAV) in backyard chickens in Africa using molecular cloning and sequence analysis to characterize CAV strains obtained from commercial chickens and Nigerian backyard chickens. Partial VP1 gene sequences were determined for three CAVs from commercial chickens and for six CAV variants present in samples from a backyard chicken. Multiple alignment analysis revealed that the 6 % and 4 % nucleotide diversity obtained respectively for the commercial and backyard chicken strains translated to only 2 % amino acid diversity for each breed. Overall, the amino acid composition of Nigerian CAVs was found to be highly conserved. Since the partial VP1 gene sequence of two backyard chicken cloned CAV strains (NGR/Cl-8 and NGR/Cl-9) were almost identical and evolutionarily closely related to the commercial chicken strains NGR-1, and NGR-4 and NGR-5, respectively, we concluded that CAV infections had crossed the farm boundary. <![CDATA[<b>Epidemiological survey on gastro-intestinal and blood-borne helminths of dogs in north-east Gabon</b>]]> A survey of helminth parasites was carried out on 198 dogs living in almost complete liberty in villages in the northeast of Gabon. Faeces and blood samples were collected and analysed. Dirofilaria immitis antigen was detected in 13.6 % of dogs using the SNAP 3Dx® test, a commercially available enzyme-linked immunosorbent assay (ELISA). Faecal examination revealed that 91.4 % of dogs were infected by intestinal helminths. Ascarids were found in 58.5 % of the samples. Trichuris vulpis was observed in 49.5 %> of cases, and Uncinaria spp. and Ancylostoma spp. in 34.8 %>, Spirocerca lupi in 25.3 % and Capillaria spp. in 10.6 %. Cestode embryophores were found in 8.6 % of the samples.