Epidemiology of Oestrus ovis (Diptera: Oestridae) in sheep in Botucatu, State of São Paulo

Abstract

The seasonal factors that influence Oestrus ovis infestation in sheep were determined in Botucatu, State of São Paulo, Southwestern Brazil, from April 2008 to March 2011. Two tracer lambs were monthly exposed to natural infestation by O. ovis larvae for 28 consecutive days, by grazing with a sheep flock. Tracer animals were then euthanized and the larvae of O. ovis recovered from nasal and sinus cavities. Of the 72 tracer lambs, 50% were infested with O. ovis larvae and the mean intensity of infestation per head infested was 16.8 larvae, with an average of 7.8 L1, 5.3 L2 and 3.7 L3. O. ovis larvae were present during the four seasons of the year, but the mean larval burden was significantly higher during the spring and summer months, compared to winter (P < 0.05). The highest rate of larvae recovery coincided with mean temperatures between 20 °C and 25 °C and air relative humidity around 70%. Results suggest that evolution and development of O. ovis practically occurs throughout the entire year, with larval infestation especially frequent during the spring and summer months.Keywords: Oestrus ovis, epidemiology, sheep. ResumoOs fatores sazonais que influenciam a infestação por larvas de Oestrus ovis, foram determinados no período de abril de 2008 a março de 2011, em ovinos criados em Botucatu, São Paulo, região Sudeste do Brasil. Mensalmente, dois cordeiros traçadores permaneceram em pastejo com um rebanho ovino durante 28 dias consecutivos, expostos à infestação natural por larvas de O. ovis. Em seguida, os cordeiros foram sacrificados, e as larvas de O. ovis recuperadas da cavidade nasal e seios frontais. Dos 72 cordeiros traçadores, 50% estavam infestados por larvas de O. ovis, com intensidade média de infestação de 16,8 larvas/cabeça infestada, com média de 7,8 L1, 5,3 L2 e 3,7 L3. As larvas de O. ovis foram recuperadas durante as quatro estações do ano, mas o número médio de larvas foi significativamente superior durante os meses de primavera e verão comparado aos meses de inverno (P < 0,05). A maior taxa de recuperação larval coincidiu com temperaturas médias entre 20 °C e 25 °C e umidade relativa do ar por volta de 70%. Os resultados sugerem que a evolução e desenvolvimento de O. ovis ocorre praticamente durante o ano inteiro, mas a infestação é mais frequente nos meses de primavera e verão.

Prevalence of Oestrus ovis(Diptera: Oestridae) in sheep from the São Paulo Central region, Brazil

“…Higher prevalence was also observed in other Brazilian studies: 85.4% in the south region of the country in sheep exposed to natural infestation for one year (RIBEIRO et al, 1990) and 50% prevalence in tracer sheep in Botucatu, State of São Paulo, Brazil (SILVA et al, 2012).…”

“…The low prevalence of oestrosis in these animals may have been influenced by previous treatment with drugs, such as macrocyclic lactones, which are usually used for the prophylaxis of infections by gastrointestinal nematodes and act against O. ovis larvae instars (DORCHIES et al, 1996(DORCHIES et al, , 1997LUCIENTES et al, 1998). The influence of anthelmintic treatment in O. ovis epidemiology was also observed in Botucatu, where reduction in the infestation of tracer sheep coincided with the treatment of flocks with macrocyclic lactones (SILVA et al, 2012).…”

“…The first study on O. ovis epidemiology in the State of São Paulo was carried out recently in Botucatu, where prevalence was 50% with mean intensity of 16.8 larvae per animal, with higher infestation rates during spring and summer (SILVA et al, 2012). The State of São Paulo presents different climatic conditions in each of its regions and small sheep farms are found in most areas of this State.…”

Oestrus ovis infection of grazing sheep during summer in southern Chile

“…Ramos et al (2006) reported no findings under 9.8°C, suggesting that the most influential factor was the temperature. Likewise, other authors agree that the optimum temperatures occur in summer and spring (Silva et al 2012). According to local meteorological records, the registered environmental conditions were optimal for the development of new infections by O. ovis in southern Chile.…”

Oestrose: uma parasitose emergente em pequenos ruminantes no Nordeste do Brasil

“…Portanto, as condições climáticas dos municípios avaliados foram ideais para o desenvolvimento do ciclo da mosca, principalmente em São Gonçalo dos Campos onde ocorreram casos em praticamente todos os meses do ano, corroborando com o que já está descrito na literatura com temperatura entre 20 a 30°C e umidade relativa do ar em torno de 70%. Nestas condições Silva et al (2012), constataram uma alta taxa de recuperação de larvas, enquanto nenhuma larva foi recuperada quando a média da temperatura mínima foi abaixo de 14 ºC.…”