Distribution of Parasitic Bovine Otitis in the Brazilian State of Mato Grosso do Sul

1. DistributionofParasiticBovine Otitis in theBrazilianStateof Mato Grosso do Sul Dr. Fernando Paiva (UFMS), Fernando de Souza Rodrigues (UFMS), Ryan Navarro (SUNY Oswego) Introduction Objective Bovine otitis is a common problem in the tropical regions of the world, frequently attributed to parasitic infections by mites of the genus Raillietia and nematodes of the genus Rhabditis. The exact impact these parasites have on the cattle industry is largely unknown and standardized treatment options have yet to be developed. However advanced cases of the disease can result in fatal neural lesions, representing a significant economic liability to the cattle industry. Therefore, this problem warrants detailed investigation. We studied the distribution of mites from the genus Raillietiain the state of MatoGrosso do Sul.Isolated mites were quantified such that the prevalence, intensity, and mean intensity values could be calculated. These values were then determined for each herd based on county of origin. This data was then complied to determine the occurrence of Raillietia sp.for the state as a whole. Theory and Methods This study was conducted in a beef slaughterhouse with the assistance of inspectors from the Ministry of Agriculturein the city of Campo Grande, MatoGrossodo Sul. One hundred thirty eight samples were obtained from slaughtered cattleduring the month of July 2012 in order to determine the prevalence and intensity of infections that cause parasitic otitis within the state. Six to ten samples were collected from animals coming from different regions. These samples were organized into herds based on their county of origin. The animal’s sex and age were also noted. The parasites were obtained from the cattle according to a technique described by previous authors. This method consisted of flushing each ear canal with pressurized water from a 50 mL syringe, and collecting the effluent back into a plastic container for laboratory analysis. In the laboratory the parasites were observed, identified, and quantified with the aid of a stereomicroscope. Mites were stored in Eppendorftubes containing a 70GL alcohol solution. These tubes were then saved for subsequent investigations. The average number of mites found in each herd was correlated to the cattle’s county of origin and age. The prevalence, intensity, and age of susceptibility for acari infestations could then be determined for the state. A. B. C. A. B. C. Figure 3. The bovineearmite, Raillietia auris. A. lateral view B. ventral view C. detailedview of anterior. BelongingtotheorderMesostigmata, R. aurisisknowntohave a global distribution whileprimarilyinfectingcattle in Brazil. It isdistinguishedfromotherspeciesofthe genus Raillietiabasedonthemorphologyofcharacteristicssuch as thegnathotectum, chelicerae, setae, and anal shield. Scale bar represents 500 µm. Figure 1. Collectionofmites. Pressurizedwater isforcedintotheauditory canal andtheeffluent isrecoveredinto a plastic container. Figure 2. Cerumenplugrecoveredfrom an animal suspectedofhavingparasiticotits. Thickmucusplugs as well as swelling are symptomsofthedisease. Results Table1. Distribution data for theprevalenceandintensityofbeefcattleparasitism by Raillietia sp. in Mato Grosso do Sul Table 1. illustrates the distribution of the acari within the state. Of the 138 animals sampled 136 were infected with Raillietia auris, yielding a state wide prevalence of 98.6%. Areas of high parasitic intensity include Bonito, Campo Grande, Corumbá, Maracaju, Nioaque, Porto Murtinho, Sidrolândia, and Terenos. Investigations into the specific factors that define these regions as high risk for infection are needed. The data in figure 4 implies that older animals are at a greater risk of parasitic infestation. These results are in accord with the findings of previous authors. The increased infections seen in the 34-38 month age group result from the animals sampled originating from the higher infection risk herds. Figure 4. The meanintensityofRaillietia sp. infestationamongstvarious age groupsofcattlesampled. Conclusion References Acknowledgements Duarte, E.R., M.M. Melo, and J.S. Hamdan (2001). Epidemiological aspects of bovine parasitic otitis caused by Rhabditis spp. and/or Raillietia spp. in the state of Minas Gerais, Brazil. Veterinary Parasitology, 101, 45-52. Duarte, E.R. and J.S. Hamdan (2004). Otitis in Cattle, an Aetiological Review. Journal of Veterinary Medicine, 51, 1-7. These results indicate that action is needed to control the increased parasitic abundance in the aforementioned high risk regions. Control measures should also be focussed on older cattle. At present, only one hundred thirty eight animals have been sampled. Data collection will continue over the following months to obtain a sample pool of 500 animals. This data will give additional insight into the extent of Raillietia sp. caused bovine otitis in MatoGrosso do Sul. Additional work is currently under way.