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

Association between Duddingtonia flagrans, dimethylsulfoxide and ivermectin for the control of Rhabditis spp. in cattle

Cattle parasitic otitis caused by the nematode Rhabditis spp. is a serious health problem in Brazil, a situation which is confounded by lack of effective control measures. In vitro studies associating biological and chemical control as an alternative method showed promising results. The objective was to evaluate the combined use of Duddingtonia flagrans (AC001), 10% dimethylsulfoxide (DMSO), and 1.9% ivermectin for the in vivo control of Rhabditis spp., in naturally infected Gyr cattle. For this purpose, 48 animals, whose infection in both ears was diagnosed, were randomly assigned to 6 groups: group 1 (ivermectin 1.9%); group 2 (10% DMSO); group 3 (AC001); group 4 (ivermectin 1.9% + 10% DMSO w/v); group 5 (1.9% ivermectin + AC001 w/v); group 6 (10% DMSO + AC001 v/v). The treatments were performed in a single dose, in the right ears, with the left ears remaining untreated, as a control group. There was a significant reduction (p < 0.01) in the number of nematodes in the treated groups in relation to the control, with the following best efficacies: groups 1 and 2, 47% and 52.9%, respectively, 7 days after treatment; groups 3, 4, and 5, 47.8%, 48.6% and 36.7%, respectively, 14 days post-treatment; group 6, 38.4%, 21 days post-treatment. It was concluded that the combination of chemical compounds and D. flagrans in a single application was effective for the in vivo control of Rhabditis spp. in naturally infected cattle.

The Genome of Caenorhabditis bovis

The free-living nematode Caenorhabditis elegans is a key laboratory model for metazoan biology. C. elegans has also become a model for parasitic nematodes despite being only distantly related to most parasitic species. All of the ∼65 Caenorhabditis species currently in culture are free-living, with most having been isolated from decaying plant or fungal matter. Caenorhabditis bovis is a particularly unusual species that has been isolated several times from the inflamed ears of Zebu cattle in Eastern Africa, where it is associated with the disease bovine parasitic otitis. C. bovis is therefore of particular interest to researchers interested in the evolution of nematode parasitism. However, as C. bovis is not in laboratory culture, it remains little studied. Here, by sampling livestock markets and slaughterhouses in Western Kenya, we successfully reisolated C. bovis from the ear of adult female Zebu. We sequenced the genome of C. bovis using the Oxford Nanopore MinION platform in a nearby field laboratory and used the data to generate a chromosome-scale draft genome sequence. We exploited this draft genome sequence to reconstruct the phylogenetic relationships of C. bovis to other Caenorhabditis species and reveal the changes in genome size and content that have occurred during its evolution. We also identified expansions in several gene families that have been implicated in parasitism in other nematode species. The high-quality draft genome and our analyses thereof represent a significant advancement in our understanding of this unusual Caenorhabditis species.

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.