An outbreak of dictyocaulosis in lactating cows on a dairy farm.
METHODS
The owner of a herd of 74 Holstein-Friesian cattle reported decreased milk production, weight loss, and coughing among lactating cows. Owner-initiated antimicrobial treatment was unsuccessful; 1 lactating cow died, and 50% of the lactating cows had clinical signs of respiratory distress, such as tachypnea and coughing.


RESULTS
On the basis of history, physical examination findings, and fecal examination results, affected animals were determined to have Dictyocaulus viviparus (lungworm) infestation. The disease history suggested that the herd contained cows with subclinical patent lungworm infestations; after introduction of susceptible heifers, the pastures had become heavily infested with D viviparus and clinical problems subsequently developed in both newly introduced and resident cows.


RESULTS
Affected and unaffected heifers and adult cows were treated with a pour-on formulation of eprinomectin (0.5 mg/kg [0.23 mg/lb]). One animal died, but 2 weeks after treatment, clinical signs among affected cattle were markedly improved. Ten weeks after treatment, milk production improved from 23 kg/cow/d (51 lb/cow/d) to 28 kg/cow/d (62 lb/cow/d).


CONCLUSIONS
The outbreak provides additional evidence that dictyocaulosis is becoming more common among adult dairy cattle, rather than almost exclusively affecting young stock. This may be attributable to anthelmintic use and management practices on dairy farms. Combined with anecdotal reports of an increase in the incidence of dictyocaulosis among adult cattle in North America, D viviparus infestation should be included as a differential diagnosis for decreased milk production, weight loss, and coughing among adult dairy cattle.
Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
Wendela
W
Wapenaar
Herman W
HW
Barkema
Maarten
M
Eysker
Ryan M
RM
O'Handley
D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D003937:Diagnosis, Differential; D004021:Dictyocaulus / Q000302:isolation & purification; D004022:Dictyocaulus Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D004196:Disease Outbreaks / Q000662:veterinary*; D005243:Feces / Q000469:parasitology; D005260:Female; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D007774:Lactation; D008168:Lung / Q000469:parasitology*; D008892:Milk / Q000378:metabolism; D010270:Parasite Egg Count / Q000662:veterinary; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D016896:Treatment Outcome
D000871:Anthelmintics; D007559:Ivermectin; C101434:eprinomectin