Prophylaxis and treatment of gastrointestinal and lungworm infections
Nov. 03, 2021
Nematode or lungworm disease in cattle is still common, especially in dairy cattle in Western Europe. In the tropics, lungworm disease is rare and only in Cuba is it considered a problem. In North America, oral disease is less important than in Europe. The disease is usually seen in calves at the end of the grazing season. However, since the early 1990s there has been a significant increase in the incidence of the disease in dairy cattle throughout Western Europe.
The population dynamics of lungworm infection are characterised by rapid spread of larvae to pasture, high pasture mortality and rapid development of immunity. This means that there is a 'race' between the accumulation of infections in susceptible cattle and resistance to these infections. The outcome determines whether the disease will occur or not.
In order to control lungworm, a good understanding of the epidemiology of the infection is required and in order to determine the epidemiology of the infection, appropriate diagnostic methods are needed.
Pathogenesis and clinical features
Bovine lungworms cause bronchitis showing large numbers of mature larvae in the bronchi and fine bronchi. Reinfection occurs as widespread eosinophilic bronchitis in adult cows (usually in the autumn). Primary infections can also occur in adult cows, resulting in significant weight loss... A typical late stage feature is the development of chronic, non-suppurative, eosinophilic granulomatous pneumonia, mainly in the caudal lobe of the lung. Considerable weight loss results and clinical recovery cases still show reduced weight gain.
Larvae may be demonstrated in faeces or oral and nasal mucus in advanced cases, and serology may confirm exposure, but the combination of epidemiological and clinical signs is usually characteristic.
Ivermectin is a member of the macrolide insecticides and is a broad-spectrum anthelmintic. It has been used successfully to control a wide range of gastrointestinal worms in domestic animals. Levamisole is also used in worm control programs with good results and frequent clinical applications.
However, since once the larvae have entered the central nervous system, significant neurological damage quickly occurs and in most cases is irreversible. Unfortunately, the infection remains asymptomatic and may go undetected at this time . Ivermectin can be used to limit the neuromigratory activity of larvae, based on the highest percentage reduction of larvae in the brain (66.7%). However, to our knowledge, there are few reports on the comparative efficacy of levamisole and ivermectin on B. transfuga larvae and whether ivermectin could have a more significant effect on their migratory activity in other organs of mice.
Affected cattle should be given a suitable dewormer and then either penned or moved to clean pastures. Their old pastures remain infected until the following summer. Improve diet to regain lost weight. Strategic deworming treatments (push injection or repeated dosing) provide good control of lungworms at the time, but have no long-term protective effect. The best prevention is the use of an oral irradiated larval vaccine (two doses in the first season, 6 and 4 weeks prior to vaccination). Enhanced immunity resulting from subsequent natural exposure may be weakened by concurrent deworming treatment and should be planned with caution.