Larvoscopic study on Dictyocaulus sp. in the faeces of beef cattle in northeastern Brazil / Estudo larvoscópico de Dictyocaulus sp. em fezes de bovinos de corte do nordeste do Brasil

Abstract The lungworm Dictyocaulus viviparus has an important role in cattle health and productivity worldwide, since infections can lead to substantial economic losses. Despite its importance, few studies investigating the epidemiological aspects of infection by this parasite have been conducted. The aim of this study was to report the occurrence of lungworm infection in beef cattle herds reared in an area of livestock production in the northeastern region of Brazil. From September 2020 to August 2021, monthly fecal samples (n = 493) were collected from 46 beef cattle. Among all the animals assessed, lungworm larvae were detected in 8.7% (4/46). None of them presented any clinical sign suggestive of infection by lungworm parasites. Twenty larvae were retrieved, with the minimum number (n = 1) detected in October and December, and the maximum number (n = 13) in November. These presented a mean length of 363 μm (± 28.65 μm) and mean width of 19 μm (± 1.03 μm), and were morphologically similar to Dictyocaulus sp.. This study reports the occurrence of this parasite in this livestock production area. Lastly, local veterinarians need to be aware of inclusion of this parasite in the differential diagnosis of other respiratory infections in beef cattle.

Resumo O parasito pulmonar Dictyocaulus viviparus tem um papel importante na saúde e produtividade bovina em todo o mundo, uma vez que infecções podem levar a perdas econômicas. Além de sua importância, poucos estudos que investigam aspectos epidemiológicos das infecções por esse parasito têm sido realizados. Objetivou-se, nesta pesquisa, relatar a ocorrência de infecção por nematódeos pulmonares em rebanhos bovinos de corte, criados em uma importante área de produção pecuária, na região Nordeste do Brasil. De setembro de 2020 a agosto de 2021, foram coletadas, mensalmente, amostras fecais (n = 493) de 46 bovinos de corte. De todos os animais avaliados, larvas de nematódeos pulmonares foram detectadas em 8,7% (4/46). Os animais não apresentaram nenhum sinal clínico sugestivo de infecção por parasitos pulmonares. Vinte larvas foram recuperadas, com o número mínimo (n = 1) detectado em outubro e dezembro, e o número máximo (n = 13) em novembro. Apresentavam comprimento médio de 363 μm (± 28,65 μm), largura média de 19 μm (±1,03 μm) e eram morfologicamente semelhantes a Dictyocaulus sp.. Este estudo relata a ocorrência desse parasito nesta área. Logo, os veterinários locais devem estar atentos à inclusão desse parasito no diagnóstico diferencial de outras infecções respiratórias em bovinos de corte.

Vaccine development and diagnostics of Dictyocaulus viviparus.

Parasitic bronchitis is a serious disease of cattle and is caused by the nematode, Dictyocaulus viviparus. For over 30 years, a radiation-attenuated larval vaccine has been used for prevention of this disease. This vaccine has been used with considerable success in the UK and parts of Western Europe, however, it has several disadvantages. It has a short shelf-life and the vaccine has to be produced annually necessitating the use of donor calves. Following vaccination, calves must receive further boosting from natural challenge to maintain protective immunity. Sales of the irradiated larval vaccine have decreased dramatically since the 1970s. This is thought to be due to increased reliance of farmers on anthelmintic programmes to control lungworm infection. It is possible that, under certain circumstances, these programmes do not allow sufficient parasite exposure to stimulate protective immunity to further Dictyocaulus challenge. This is borne out by the recent documented increase in the number of outbreaks of parasitic bronchitis in the UK. A stable vaccine against D. viviparus that is capable of stimulating a more prolonged immunity would be beneficial. Recent research has been directed at identification and isolation of components thought to be involved in parasite survival in the host and examination of their potential as vaccine candidates. One of these components is acetylcholinesterase (AChE), an enzyme secreted by adult worms. This review describes the development of the secreted AChE as a vaccine candidate, as well as documenting recent developments in the immunodiagnosis of D. viviparus.

Diagnosis of causes of respiratory diseases in cattle.

Cattle with Pasteurella bronchopneumonia usually have a fever, abnormal respiratory sounds in the cranioventral lung fields, consolidation, pleuritis and abscesses. Lungworms primarily affect 4- to 6-month-old calves, which become febrile and dyspneic, with moist rales. Diagnosis is by fecal examination using the Baermann technic. Proliferative pneumonia usually affects stabled adults, which develop severe dyspnea and tachypnea. Diagnosis is by the history, clinical signs and lung biopsy. Acute bovine pulmonary emphysema is caused by ingestion of large amounts of L-tryptophan in lush pasture. Affected cattle have severe, acute dyspnea, an expiratory grunt and froth around the muzzle. Diagnosis is by the history and clinical signs. Bronchiolitis obliterans narrows the airways of older animals to cause dyspnea. A positive response to corticosteroids aids diagnosis. Anaphylaxis occurs in cattle of all types and ages and is precipitated by various antigens in a type-I hypersensitivity reaction. Use of atropine aids diagnosis. Allergic or hypersensitivity pneumonia is caused by an allergy to insecticides, dead ascarid larvae or the mold, Micropolyspora faeni. Diagnosis is by a history of insect fogger use, finding M faeni in the forage, and typical histologic lesions in lung samples. Cattle with caudal vena caval thrombosis have dyspnea, a fever, froth around the muzzle, an expiratory groan and hypergammaglobulinemia. Malignant catarrhal fever is diagnosed by a history of previous exposure to sheep and finding swollen lymph nodes, fever, neutropenia and arteritis.

The incidence of Dictyocaulus viviparus infections in cattle in The Netherlands. I. The Enzyme Linked Immunosorbent Assay as a diagnostic tool.

The Enzyme Linked Immunosorbent Assay (ELISA) provides a very efficient technique for detecting antibodies against Dictyocaulus vivparus in calves. Although low level cross reactions were found in animals with gastrointestinal nematodes, the specificity and sensitivity of the technique are sufficient for herd diagnosis of lungworm infections and for survey work. This conclusion is reached on the basis of artificially and naturally infected calves. ELISA titres correlate well with Indirect Haemagglutination titres, parasitological findings, and clinical observations.