In the lab of cetacean ecology in CICIMAR (La Paz, Mexico) we have lately published a short communications about quantitative parasitology in blue whales… Flores-Cascante, L. and Gendron, D. 2012. Application of McMaster's technique in live blue whale. Veterinary Record;171:9 220 doi:10.1136/vr.100749 (dgendron@ipn.mx) Summary: Due to field sampling constrictions, studies on the intestinal parasite load in free ranging cetaceans is lacking. Reports on cetacean parasites have generally been obtained from stranded and harvested animals and thus cannot be considered representative of the “normal’ population. In the case of the blue whale, Balaenoptera musculus few descriptions of the parasitic fauna exist and the information is qualitative. Standardized methodologies are essential to evaluate the baseline data on the population's parasite load, as well as on the relationship between parasite and host, and to optimize long-term study. Here we report the use and optimization of the McMaster technique for the quantization of parasite eggs in feces of terrestrial mammals as applied to the blue whale. We collected 30 feces samples of blue whales during our 2009-2011 winter-spring fieldwork in the southwestern Gulf of California, Mexico. Subsample of feces were collected opportunistically at the sea surface and were preserved in formalin at 5 % and dehydrated for 24hrs. The flotation solution, Zinc Sulfate was chosen over the modified Sheather’s Solution since the transparency allowed better observation of the eggs. The effective sample size was estimated using 0.3, 0.5 and 1gr of dried feces. No significant difference in the count of egg parasites per gram of dry feces (EPG) was found between sample sizes (p> 0.05), and the parasite load was estimated from 0.5 gram at the Helminth level. The average intensity was 356 EPG ranging from 100 to 1250 and corresponded to 19 different blue whale individuals. Three individuals were re-sampled more than once during one season and EPG counts were constant (p>0.05). Adult acanthocephalans of the genus Bolbosoma sp were found in the samples, a genus previously reported for the Northeastern Pacific blue whales. The use of the McMaster technique to assess parasite load in blue whales offers an important new parameter that can be easily monitored. Regards, Lavinia. ----------------------------- Biol. Mar. Lavinia F. Cascante Estudiante de M.C. en Manejo de Recursos Marinos Laboratorio de Cetáceos y Quelonios CICIMAR - IPN La Paz, BCS. México La información de este correo así como la contenida en los documentos que se adjuntan, pueden ser objeto de solicitudes de acceso a la información.