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

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Abstract:

Eighty-eight percent of adult beluga whales, Delphinapterus leucas (age 7 years; n = 32), and 72% of juveniles (1 year age < 7 years; n = 11) were infected with the cranial sinus nematode Pharurus pallasii. No fetuses or young of the year (age 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.

Au cours de notre étude, 88 % des bélugas adultes (âge 7 ans; n = 32) et 72 % des juvéniles (1 âge < 7 ans; n = 11) étaient infectés par le nématode des sinus crâniens, Pharurus pallasii. Aucun foetus ni jeune de l'année (âge 1 an; n = 9) n'était infecté. L'intensité moyenne des infections chez les adultes était de 419 (étendue 2–2042) et de 179 chez les juvéniles (étendue 1–500). Il n'y avait pas de différence significative entre l'intensité moyenne des infections des mâles et celle des infections des femelles, ni entre celle des infections des bélugas juvéniles et celle des infections des bélugas adultes. L'absence d'infection chez les jeunes de l'année laisse croire que la transmission n'est pas transplacentaire ni transmammaire et que les infections sont acquises lorsque les jeunes bélugas commencent à manger des proies infectées. Les P. pallasii étaient 3 fois plus nombreux dans les sinus péribullaires que dans les sinus frontaux, mais répartis également des deux côtés. Les mâles et les femelles de P. pallasii étaient significativement plus longs dans les sinus très infectés que dans les sinus légèrement infectés. La fécondité des femelles gravides n'était pas affectée par l'intensité des infections. Aucune lésion macroscopique n'a été observée en association avec P. pallasii, ni dans les carcasses fraîches, ni dans les carcasses congelées. Le faible nombre des P. pallasii adultes dans les poumons fait croire que les sinus crâniens constituent leur site d'infection favori. Aucune relation n'a été établie entre l'intensité des infections et la condition physique des bélugas.

Document Type: Research Article

Publication date: March 1, 2003

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