Luís Alberto Ambrósio

F200Y polymorphism in the β-tubulin gene in field isolates of Haemonchus contortus and risk factors of sheep flock management practices related to anthelmintic resistance

Haemonchus contortus is the most prevalent and pathogenic nematode of sheep in tropical areas. The objectives of this study were to assess the frequency of the F200Y polymorphism on the β-tubulin gene in third-stage larvae of H. contortus from 33 sheep flocks in São Paulo state, Brazil, and to associate this frequency to risk factors based on farm management practices. The resistance allele frequency varied from 9 to 74%, and the resistance genotype frequency varied from 0 to 66.7%. Resistance genotype frequencies higher than 40% were associated with multiple risk factors - new sheep farming enterprises, the absence of farm records, the use of Dorper and Suffolk breeds, rotational grazing, the lack of wetlands on farms, pasture sharing with cattle or horses, frequent incorporation of animals into the flock, semi-intensive farming systems, whole-flock treatment, failure to use the FAMACHA method, lack of the dose-and-move practice, anthelmintic rotation after each application, visual estimation of animal weight for treatment, and lack of drug combination use. It can be concluded that genotyping the F200Y polymorphism can be used to monitor the resistance in sheep flocks and the knowledge of management strategies at the farm level is important to identify drug resistance related factors.

Management and control of parasites on dairy farms in northwestern region of São Paulo state

Dairy cattle farming is of great economic and social importance in all Brazilians regions. Parasites can reduce milk productivity, especially the tick Rhipicephalus (Boophilus) microplus. This study consisted of a questionnaire answered by 40 milk producers in the northwestern region of the State of São Paulo. The aim was to ascertain how these producers controlled ticks and other parasites. Very many of them knew nothing about the biological cycle of the cattle tick or about strategic control or acaricide efficacy tests. The majority (87.5%) controlled ticks at a high frequency, without technical criteria and care to apply the acaricide. Spraying was the most used mode of acaricide application (95%) and endectocides were used by 45%. Cattle tick fever was the harm most associated with ticks (87.5%) followed closely by screwworm (77.5%). However, 65% were satisfied with their tick control. About the control of others parasites, all dewormed at least twice a year their animals; 65% were controlling horn fly; 40% had problems with screwworm. The interviewers had in general good level of education and the farms generally exhibited a high degree of technology for milk production on pasture because half of them received technical assistance frequently.