Epidemiology of bovine parasitic otitis

Combined use of ivermectin, dimethyl sulfoxide, mineral oil and nematophagous fungi to control Rhabditis spp

Rhabditis spp., is a nematode known to cause otitis externa, an infection difficult to control, in cattle reared within tropical regions. The objective of this study was to assess the combined use of ivermectin 1%, dimethyl sulfoxide 1% and mineral oil 100% containing nematophagous fungi of both Duddingtonia flagrans (AC001) and Monacrosporium thaumasium (NF34) species to control in vitro Rhabditis spp. Thus, 12 experimental groups were designed with eight replicates each: G1 (nematodes + AC001); G2 (nematodes + NF34); G3 (nematodes + ivermectin 1%/positive control); G4 (nematodes + dimethyl sulfoxide 1%/positive control); G5 (nematodes + mineral oil 100%/positive control); G6 (nematodes + AC001 + ivermectin 1%); G7 (nematodes + NF34 + ivermectin 1%); G8 (nematodes + AC001 + mineral oil 100%); G9 (nematodes + NF34 + mineral oil 100%); G10 (nematodes + AC001 + dimethyl sulfoxide 1%); G11 (nematode + NF34 + dimethyl sulfoxide 1%); G12 (nematode + distilled water/negative control). The results demonstrated that all experimentally treated groups differed statistically (p < 0.01) from the control group. In the present study, the use of dimethyl sulfoxide 1% and mineral oil 100% in conjunction with conidia fungi portrayed noteworthy outcomes, which represents a future premise for the combined use of nematophagous fungi within these vehicles in both controlling Rhabditis spp.

Detecção e tratamento de otite por Rhabditis blumi em bovinos da região Norte do Brasil

Resumo: O presente estudo teve como objetivo descrever a ocorrência de otite parasitária causada por Rhabditis blumi em bovinos leiteiros de raça Gir de uma fazenda da região Norte do Brasil. Foram coletadas amostras de 42 bovinos por swab e lavado dos condutos auditivos externos (CAE). Ao exame clínico, 9,5% (4/42) dos bovinos apresentavam sintomatologia nervosa, como leve a moderada rotação da cabeça, apatia, flacidez dos lábios e ptose palpebral unilateral, alopecia das regiões da cabeça e cupim, causados pelo desconforto e prurido da região auricular, alteração na mastigação e acúmulo de alimento na cavidade oral. Adicionalmente, 71,4% (30/42) dos abovinos mostraram a presença do parasita no cerúmen dos condutos auditivos. À análise microscópica do material do saco conjuntival foi observado presença do parasita em 90% (9/10) dos bovinos avaliados. Os 30 bovinos positivos para Rhabditis spp. foram distribuídos aleatoriamente em três grupos de 10 animais: (G1) Bovinos controle, (G2) Bovinos tratados com ivermectina 1% pour on e (G3) Bovinos submetidos a lavado dos condutos auditivos externos (CAE). Cada tratamento foi repetido três vezes com intervalo de sete dias. No G1 os 10 bovinos mantiveram-se infectados durante todo o estudo. No G2 20% dos bovinos foram negativos após os dois primeiros tratamentos, porém, mostraram-se positivos na terceira avaliação. No G3 todos os bovinos mantiveram-se positivos, sendo observada apenas diminuição da carga parasitária. A identificação por análise molecular por meio de fragmentos amplificados da expansão D2/D3 do 28S rDNA confirmou a presença apenas da espécie Rhabditis blumi nos animais. Baseado nas observações clínicas, morfológicas e moleculares pode-se relatar o primeiro caso de R. blumi em bovinos da raça Gir no Estado do Pará, através da compra de animais oriundos de áreas onde a otite parasitária tem sido diagnosticada, principalmente de Minas Gerais, para formar animais mestiços (Gir x Holandês). Desta forma ressalta-se a importância do exame clínico prévio dos animais a serem transferidos para outras propriedades ou regiões. Este relato também parece ser o primeiro sobre a presença de R. blumi no saco conjuntival de bovinos. O tratamento com ivermectina no G2 não surtiu melhora clínica dos bovinos.

Inefficacy of albendazole sulphoxide and ivermectin for the treatment of bovine parasitic otitis caused by rhabditiform nematodes

The purpose of this study was to evaluate the efficacy of orally administered albendazole sulphoxide and pour-on ivermectin for the treatment of bovine parasitic otitis caused by rhabditiform nematodes. Eighteen Gyr cows presenting clinical otitis were divided in three groups with six animals each. The first one did not receive any treatment (control group). The second one was treated with 0.5% pour-on ivermectin, 500µg/kg of body weight, and the third group was treated with oral 6% albendazole sulphoxide, at 6.0mg/kg. Both ear canals of each animal were reexamined on days 7 and 21 post treatment. The animals in the control group remained infected throughout the days of observation. Ivermectin treatment did not show effectiveness on days 7 or 21 post treatment. The albendazole sulphoxide treatment had an efficacy of 16.7 and 25% on days 7 and 21, respectively. Further studies are required to assess an effective treatment for this parasitic disease, especially via alternative administration routes, because of its significant impact on Bos taurus indicus cattle breeding in Tropical and Subtropical Regions.

Otitis in cattle, an aetiological review

Otitis externa in cattle has a significant impact in tropical and subtropical regions, and the aetiological agents are predominantly rhabditiform nematodes and mites of the genus Raillietia. Its prevalence is higher in mature and Zebu cattle. In advanced clinical cases there can be irreversible and fatal neural lesions. Ear infection in calves has been associated with concurrent respiratory diseases and mixed infection. The principal reported agents of otitis in calves are bacteria such as Actinomyces spp., Corynebacterium pseudotuberculosis, Escherichia coli, Haemophilus somnus, Pasteurella multocida, Mannheimia haemolytica, Pseudomonas spp., Streptococcus spp. and Mycoplasma bovis. The control and treatment of bovine otitis is not standardized and there is little evidence-based support for the diverse treatments available in the literature.

Factors associated with the prevalence of Malassezia species in the external ears of cattle from the state of Minas Gerais, Brazil

Swabs collected from the external ears of 942 cattle, including both European and zebu breeds, were used to evaluate the epidemiology of Malassezia species. High numbers of Malassezia isolates were significantly associated with maturity of the animals and with diagnosed otitis. In healthy animals, a particularly low prevalence of the genus was found in Holstein cows, especially in the summer months, a finding perhaps correlating with the open, air-exposed ears of this breed. Pendutlous-eared zebu breeds and hybrids had higher levels of colonization, although this effect was more pronounced in humid regions, and was least in the dry north and west of the state. The most common species seen was M. sympodialis, which accounted for 47.1% of isolates from healthy cattle and 39.1% from cattle with otitis. In cattle with otitis sampled in summer, we found that the relatively thermotolerant M. sympodialis made up 80.8% of isolates. By contrast, during the winter the less thermotolerant M. globosa was the most common species from otitis, making up 56% of the isolates. Humidity and temperature may be the main factors explaining the epidemiology of Malassezia diseases and colonizations in both animals and humans.

Epidemiological aspects of bovine parasitic otitis caused by Rhabditis spp. and/or Raillietia spp. in the state of Minas Gerais, Brazil

The occurrence of bovine external otitis in tropical regions is predominantly assigned to parasitic infections by rhabditiform nematodes and infestations by mites of the genus Raillietia. This research had the purpose of investigating the prevalence of parasitic otitis in the dry and rainy seasons of Minas Gerais and correlating it with variables age, breed and the presence of horns. The secretion or cerumen of 981 cattle was collected with sterile swabs, placed in test tubes and exposed to sunlight for the identification of clinical infections caused by rhabditiform nematodes. The ear canals of 109 animals were flushed to study the occurrence of mites of the genus Raillietia. Clinical otitis caused by rhabditiform nematodes was observed only in animals of the Gyr breed, affecting 169 (60.1%) of the total (278) of these cattle. The prevalence of otitis in this breed was significantly higher for mature adult cows (P<0.001) and in cows with horns (P<0.001). In a total of nine animals suspected of raillietiosis, the examinations revealed the presence of Raillietia spp. in two Dutch cows. These results demonstrate that treatment must be focused on adult Gyr cattle with horns. This and future studies with an emphasis on epidemiological aspects may contribute to development of alternative approaches to reduce disease.

Clinical observations on bovine parasitic otitis in Tanzania

Between January 1982 and December 1989 more than 5,000 clinical cases of bovine parasitic otitis were examined. Clinical signs were mild in early cases and were characterised by dullness, anorexia and occasional head shaking, but were severe in long standing cases where the major presenting clinical signs were dark brown aural discharges which soiled the hair below and in front of the ear, emaciation, central nervous signs, recumbency and death.

Field control of bovine parasitic otitis

Nicotine used at approximately 2 ppm in 0.25% toxaphene dip wash was found to be 95% effective in the treatment and control of bovine parasitic otitis after dipping clinically affected cattle twice weekly for twelve weeks. Only three of 64 clinically affected animals failed to recover completely following the above treatment regime. The viable nematodes, Rhabditis bovis, which were easily isolated from dip tanks prior to treatment, could no longer be isolated 48 hours following dip tank treatment with nicotine. The above results are very significant since the control of bovine parasitic otitis would greatly enhance the productivity of cattle.