Melbourne Veterinary School - Research Publications
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ItemA Molecular Diagnostic Tool to Replace Larval Culture in Conventional Faecal Egg Count Reduction Testing in Sheep(PUBLIC LIBRARY SCIENCE, 2012-05-22)The accurate diagnosis of parasitic nematode infections in livestock (including sheep and goats) is central to their effective control and the detection of the anthelmintic resistance. Traditionally, the faecal egg count reduction test (FECRT), combined with the technique of larval culture (LC), has been used widely to assess drug-susceptibility/resistance in strongylid nematodes. However, this approach suffers from a lack of specificity, sensitivity and reliability, and is time-consuming and costly to conduct. Here, we critically assessed a specific PCR assay to support FECRT, in a well-controlled experiment on sheep with naturally acquired strongylid infections known to be resistant to benzimidazoles. We showed that the PCR results were in close agreement with those of total worm count (TWC), but not of LC. Importantly, albendazole resistance detected by PCR-coupled FECRT was unequivocally linked to Teladorsagia circumcincta and, to lesser extent, Trichostrongylus colubriformis, a result that was not achievable by LC. The key findings from this study demonstrate that our PCR-coupled FECRT approach has major merit for supporting anthelmintic resistance in nematode populations. The findings also show clearly that our PCR assay can be used as an alternative to LC, and is more time-efficient and less laborious, which has important practical implications for the effective management and control strongylid nematodes of sheep.
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ItemOriental theileriosis in dairy cows causes a significant milk production loss(BIOMED CENTRAL LTD, 2014-02-19)BACKGROUND: Oriental theileriosis is a tick-borne, protozoan disease of cattle caused by members of the Theileria orientalis-complex. Recent outbreaks of this disease in eastern Australia have caused major concerns to the dairy and beef farming communities, but there are no published studies of the economic impact of this disease. On a farm in Victoria, Australia, we assessed whether oriental theileriosis has an impact on milk production and reproductive performance in dairy cows. METHODS: Blood samples collected from all 662 cows on the farm were tested using an established molecular test. For individual cows, milk production and reproductive performance data were collected. A clinical assessment of individual cows was performed. Based on clinical findings and molecular test results, the following groups of cows were classified: group 1, with cardinal clinical signs of oriental theileriosis and molecular test-positive for T. orientalis; group 2, with mild or suspected signs of theileriosis and test-positive; group 3, with no clinical signs and test-positive; and group 4, with no clinical signs and test-negative. Milk production and reproductive performance data for groups 1, 2 and 3 were each compared with those for group 4 using linear and logistic regression analyses, respectively. RESULTS: At 100 days of lactation, group 1 cows produced significantly less milk (288 l; P = 0.001), milk fat (16.8 kg; P < 0.001) and milk protein (12.6 kg; P < 0.001) compared with group 4. At this lactation point, group 2 also produced significantly less milk fat (13.6 kg; P = 0.002) and milk protein (8.6 kg; P = 0.005) than group 4. At 305 days of lactation, group 1 cows produced significantly less milk (624 l; P = 0.004), milk fat (42.9 kg; P < 0.001) and milk protein (26.0 kg; P < 0.001) compared with group 4 cows. Group 2 cows also produced significantly less milk fat (21.2 kg; P = 0.033) at this lactation point. No statistically significant difference in reproductive performance was found upon pairwise comparisons of groups 1-3 with group 4 cows. CONCLUSIONS: The present findings demonstrate that clinical oriental theileriosis can cause significant milk production losses in dairy cattle.
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ItemEpidemiological survey following oriental theileriosis outbreaks in Victoria, Australia, on selected cattle farms(ELSEVIER, 2013-11-08)This study investigated Theileria orientalis following outbreaks of oriental theileriosis in cattle in the state of Victoria, Australia, from September 2010 to January 2012, using traditional and molecular methods of diagnosis. A questionnaire was used to collect epidemiological information from cattle farms. Blood samples (n=301), collected from individual symptomatic and asymptomatic cattle from 19 cattle farms, were examined for the presence of Theileria on stained blood smears and tested using a PCR-based approach, employing a region within the major piroplasm surface protein (MPSP) gene as a marker. The microscopic examination of stained blood smears detected stages consistent with Theileria piroplasms in 28.1% (79/281) of the samples. PCR products were amplified from 70.8% (213/301) of the samples. Mutation scanning analysis of all amplicons displayed seven distinct profiles. Following the direct sequencing of representative amplicons, the genotypes ikeda, chitose, buffeli and type 5 were detected in 91.1%, 32.9%, 2.4% and 1.4% of 213 blood samples, respectively. The distribution of these four genotypes varied among the 19 farms; genotype ikeda was detected on all farms, whereas genotypes chitose, buffeli and type 5 were detected on 14, 3 and 2 farms, respectively. Mix infections with genotypes ikeda and chitose were common (21.6%). Survey results revealed that oriental theileriosis affected mainly beef cows of more than two years of age, prior to calving, and disease was associated with abortion and cow deaths. Future investigations should focus on developing improved tools for investigating and managing oriental theileriosis.