Desenvolvimento e migraÇão de larvas infectantes de ciatostomíneos (Nematoda: Cyathostominae) em gramínea coast cross (Cynodon dactylon) em clima tropical, na Baixada Fluminense, RJ, Brasil

Abstract

ResumoEsse estudo foi realizado no período de julho de 2003 a novembro de 2004, para avaliar o desenvolvimento, a sobrevivência, a migração das larvas infectantes em gramínea "coast cross" (Cynodon dactylon) e o horário de maior disponibilidade, em condições de clima tropical, na Baixada Fluminense, RJ, Brasil. De julho de 2003 a setembro de 2004, massas fecais de equinos naturalmente infectados foram depositadas mensalmente sobre a gramínea. Sete dias após, amostras de fezes e gramínea foram coletadas semanalmente em diferentes horários (8, 13 e 17 horas), pesadas e processadas pela técnica de Baermann. O desenvolvimento, a sobrevivência e a migração das larvas infectantes nas fezes e na gramínea foram observados durante todo o período. A sobrevivência das L 3 foi de até 15 semanas nas fezes e 12 semanas na gramínea no período seco e de nove e oito semanas, respectivamente, para o período chuvoso. No período chuvoso, maior número de L 3 foi recuperado nas fezes e, no período seco, na gramínea. Condições climáticas influenciaram diretamente o número larvas infectantes. Pela análise multivariada, ficou demonstrado uma forte relação entre o tempo e o número de L 3 nas fezes, sendo esta relação menos acentuada para a gramínea. Não se observou diferença significativa entre os horários de coleta.Palavras-chave: Cyathostominae, equinos, migração, coast cross, clima tropical. AbstractA study following the development and migration of Cyathostominae infective larvae was conducted from July 2003 to November 2004 in tropical climate, Baixada Fluminense, RJ, Brazil. Samples of naturally infected feces were placed on 12 m 2 plot each month on a cyathostomin-free "Bermuda grass" pasture (Cynodon dactylon). After Seven days, samples of feces and grass were collected every week at 8 a.m, 1 and 5 p.m., weighed and processed by Baermann technique. Higher survival of L 3 was found at dry season, 15 and 12 weeks on feces and sward respectively, at rainy season the survival was smaller. The multivariable analysis of main components was evident the influence of time and environment variables on L 3 recovery from feces and grass. Close relationship between time and the number of L 3 in feces could be noted, in contrast with L 3 in sward. The climatic conditions influenced directly the number of infective larvae. The infective larvae were recovered during three times and the Kruskal-Wallis test did not present significance among them.

Seasonality and Dynamics of Gastrointestinal Helminths in Grazing Horses

“…In the current study, the season that presented the highest precipitation (summer) also had the highest EPG counts (Table 1). These results agree with those found by Couto et al [38], who observed that in the rainy season, in tropical climates (high temperature), horses presented higher EPG counts, which may be related to greater egg elimination by female horses when weather conditions are more favorable.…”

Cyathostomin larvae: presence on Brachiaria humidicola grass during the rainy and dry seasons of Brazil

“…The type of grass can also affect the number of larvae recovered. Other studies with different grasses in the same study area reported a lower number of larvae recovered from Coast-cross and Tifton 85 pastures (BEZERRA et al, 2007;COUTO et al, 2008;COUTO et al, 2009;QUINELATO et al, 2008;SANTOS et al, 2011) than from Brachiaria humidicola in our study. Pastures are more fibrous and flattened during the dry season and, depending on the management, they can protect L 3 against temperature changes and evaporation (BRADY; WEIL, 1999), providing an ideal microclimate for a prolonged survival.…”

“…Fecal masses play an important role in the development of eggs and larvae, acting as reservoirs for larvae, as observed by Mfitilodze and Hutchinson (1987), Uhlinger (1991), Bezerra et al (2007) and Santos et al (2011). With adequate humidity and temperature, horses can become infected immediately after rainfall, but these animals in this area are more exposed to infection during dry than heavy rainfall periods (BEZERRA et al, 2007;QUINELATO et al, 2008;COUTO et al, 2008;COUTO et al, 2009;RODRIGUES et al, 2008). The environmental conditions of the study area favor the development of infective cyathostomin larvae, i.e., L 3 were present in the pasture during both periods studied.…”

“…Thus, there is a need to know the epidemiology of these parasites and their interaction with the host to establish effective control strategies. Studies of the prevalence of cyathostomin larvae in pastures using different grasses have been performed in Brazil by Bezerra et al (2007) (Tifton 85), Couto et al (2009) (Coast cross) and Santos et al (2011) (Brachiaria humidicola). It is essential to find alternative control methods to minimize the use of anthelmintics due to cyathostomin resistance to different groups of chemicals.…”