Distribution of Parasitic Bovine Otitis in the Brazilian State of

Mato Grosso do SulDr. Fernando Paiva (UFMS), Fernando de Souza Rodrigues (UFMS), Ryan Navarro (SUNY Oswego)

Conclusion References Acknowledgements

Introduction

Theory and Methods

Objective

Results

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 Raillietia in the state of Mato Grosso 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.

This study was conducted in a beef slaughterhouse with the assistance of inspectors from the Ministry of Agriculture in the city of Campo Grande, Mato Grosso do Sul. One hundred thirty eight samples were obtained from slaughtered cattle during 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 Eppendorf tubes containing a 70 GL 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.

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.

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 Mato Grosso do Sul. Additional work is currently under way.

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 thestate of Minas Gerais, Brazil. Veterinary Parasitology, 101, 45-52.

Duarte, E.R. and J.S. Hamdan (2004). Otitis in Cattle, anAetiological Review. Journal of Veterinary Medicine, 51, 1-7.

Figure 4. The mean intensity of Raillietia sp. infestation amongst various age groups of cattle sampled.

0

20

40

60

80

100

120

Intensity of Raillietia sp. by Age

Age of Cattle in Months

Ave

rage

Num

ber o

f Mite

Infe

stati

on

24-28 28-34 34-38 38-42 48-54 54

Prevalence (%)

Intensity Range (individual mites)

Mean Intensity (individual mites)

Água Clara 100 5-74 19.9Bonito 100 21-130 65.2

Brasilândia 100 11-87 48.8Camapuã 100 6-207 37.0

Campo Grande 100 26-194 70.4

Cassilândia 100 9-28 21.6Corumbá 100 71-121 94.4Dourados 100 3-65 22.4Ivinhema 62.5 1-7 3.6Jaraguari 100 2-33 12.0Maracaju 100 35-139 79.3Nioaque 100 54-129 95.0

Porto Murtinho 100 4-245 63.3

Ribas do Rio Pardo 100 8-30 16.7

Rochedo 100 8-50 27.3Sidrolândia 100 4-195 67.3

Terenos 100 9-127 56.0Mato Grosso do

Sul98.6 1-245 47.6

Table 1. Distribution data for the prevalence and intensity of beef cattle parasitism by Raillietia sp. in Mato Grosso do Sul

Figure 1. Collection of mites. Pressurized wateris forced into the auditory canal and the effluent is recovered into a plastic container.

Figure 2. Cerumen plug recovered froman animal suspected of having parasitic otits. Thick mucus plugs as well as swelling are symptoms of the disease.

Figure 3. The bovine ear mite, Raillietia auris. A. lateral view B. ventral view C. detailed view of anterior. Belonging to the order Mesostigmata, R. auris is known to have a global distribution while primarily infecting cattle in Brazil. It is distinguished from other species of the genus Raillietia based on the morphology of characteristics such as the gnathotectum, chelicerae, setae, and anal shield. Scale bar represents 500 µm.

A. B. C.A. B. C.