Lungworm (Pharurus pallasii: Metastrongyloidea: Pseudaliidae) infection in the endangered St. Lawrence beluga whale (Delphinapterus leucas)

Abstract

Eighty-eight percent of adult beluga whales, Delphinapterus leucas (age [Formula: see text]7 years; n = 32), and 72% of juveniles (1 year [Formula: see text] age < 7 years; n = 11) were infected with the cranial sinus nematode Pharurus pallasii. No fetuses or young of the year (age [Formula: see text]1 year; n = 9) were infected. The mean intensity of infection was 419 (range 2–2042) in adults and 179 (range 1–500) in juveniles. There was no difference in mean intensity of infection between the sexes or between juvenile and adult beluga. The absence of P. pallasii in young of the year suggests that transmission is not transplacental or transmammary and that infections are acquired as young beluga begin to feed on infected prey. Pharurus pallasii were 3 times more numerous in the peribullar sinuses than in the frontal sinuses, but were equally distributed laterally. Male and female P. pallasii in heavily infected sinuses were significantly longer than those in lightly infected sinuses. No intensity-dependent effect on fecundity of gravid females was observed. No macroscopic lesions were observed in association with P. pallasii in fresh or frozen carcasses. Low numbers of adult P. pallasii in the lungs suggest that the cranial sinuses are the preferred site of infection. No relationship was found between intensity of infection and body condition of beluga.