What do young beluga whales die of?
The analysis of beluga whale carcasses found along the shores of the St. Lawrence between 1983 and 1999 led researchers to establish the chief causes of death of individuals within this population. These include cancers, gastro-intestinal and respiratory infections, bacterial, viral and protozoan infections. In a recent study, cases of verminous pneumonia (pneumonia caused by lungworms) were re-examined.
To go through the looking glass
The study was conducted on 117 beluga whale carcasses found along the shores of the St. Lawrence Estuary. The two most common lungworm species were Stenurus arctomarinus and alocercus monoceris. Adult S. arctomarinus worms are visible to the naked eye and are usually found between the bronchial tubes of cetaceans, sometimes accompanied by inflammation. Adult Halocercus sp. Worms, on the other hand, are harder to detect, necessitating the microscopic examination of pulmonary tissue.
In all, 14.5 percent of the beluga whales examined succumbed to verminous pneumonia; most of these deaths occurred in immature animals. The Halocercus species was generally more abundant in immature beluga whales than in other age groups. Adult worms were even found in the lungs of beluga whales less than one year old; it is therefore likely that the parasite can be transmitted from mother to young through the placenta or mother’s milk. Conversely, the vast majority of these parasites are in all likelihood acquired when beluga whales ingest intermediate hosts (fish) that contain infectious larvae. In short, lungworm infections have been identified as the probable cause of death of over 40 percent of reported deaths in the one to seven year age group. Parasitic diseases are probably a major cause of death of young beluga whales, which represent the future of the entire population.
Stéphane Lair and Bérengère Wyrzykowski, Canadian Cooperative Wildlife Health Centre and Centre québécois sur la santé des animaux sauvages.
Lena Measures, Fisheries and Oceans Canada, the University of Montreal’s Fonds Aqua Santé du Saint-Laurent
LAIR, S. et B. WYRZYKOWSKI, 2005. Verminous pneumonia in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary. Canadian Cooperative Wildlife Health Centre Newsletter, Vol. 4 no. 1 pp. 7-8.