Seasonal prevalence and intensity of hookworms (Uncinaria spp.) in California sea lion (Zalophus californianus) pups born in 2002 on San Miguel Island, California.

Intestines of California sea lion (Zalophus californianus) pups (n= 204), born in 2002 on San Miguel Island, California, were examined for hookworms (Uncinaria spp.) as part of a seasonal mortality study from June through December 2002 and January 2003. The investigation was planned to coincide with most of the previously established hookworm infection period of the pups. Prevalence of hookworms in dead pups was 100% for each month of the study. The geometric mean intensity of infections per month was: 94.03 (n=30) for June, 629.09 (n=50) for July, 319.90 (n=31) for August, 159.90 (n=30) for October, 109.03 (n=30) for November, 37.84 (n=24) for December 2002 and 11.05 (n=9) for January 2003. In addition to the temporal pattern, the infection intensity was higher for pups in good condition and for male pups. An inter-year comparison of hookworm counts from dead pups collected in July of 1996, 2000, and 2002 also demonstrated higher intensity in pups in better condition but sex-differences in intensity were inconsistent across years. The inter-year comparison also demonstrated higher intensities in dead pups collected from portions of the rookery with sandy substrate versus rocky substrate. No annual differences in intensity were found after adjusting for substrate and condition.

Observations in 2001 on hookworms ( Uncinaria spp.) in otariid pinnipeds.

Uncinaria spp. were recovered from the milk of California sea lions ( Zalophus californianus) collected from the: (1) teats of a cow just after parturition (one parasitic third-stage larva, L(3)), (2) stomach of her nursing pup (two L(3)), and (3) stomach of a dead pup about 2 days old (one L(3), one headless, probably L(3), and four L(4)) on San Miguel Island, California in May 2001. This, in addition to earlier research, indicates transmammary transmission of hookworms in this host. Uncinaria spp. were found in dead northern fur seals ( Callorhinus ursinus) in the: (1) intestines of 2 of 75 pups (either one or two adult specimens in each infected pup) and (2) ventral abdominal blubber of 3 of 78 subadult males (one to seven L(3) in each infected seal) on St. Paul Island (SPI), Alaska in July and August 2001. These findings verify the low current prevalence of Uncinariaspp. in fur seals on SPI. Rectal fecal samples taken from 50 live Steller sea lion ( Eumetopias jubatus) pups, about 1 month old, on Rogue Reef in Curry County, Oregon in July 2001, were all negative for the eggs of Uncinaria spp. The apparent zero infection rate in these pups is possibly because the rocky terrain of this rookery is not suitable for hookworm transmission.

Current prevalence of adult Uncinaria spp. in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus) pups on San Miguel Island, California, with notes on the biology of these hookworms.

A prevalence survey for hookworms (Uncinaria spp.) was done in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus) pups on San Miguel Island, CA, in 2000. Intestines of dead pups were examined for adult hookworms in July. These parasites were found in 95% of 20 fur seal pups and 100% of 31 sea lion pups. The number of hookworms varied from 4 to 2142 (mean = 760) in fur seal pups and from 20 to 2634 (mean = 612) in sea lion pups. A direct relationship was evident between body condition and number of hookworms in the pups; that is, pups in poor condition had fewer hookworms than those in good condition. There was a decline in the number of hookworms in sea lion pups in 2000 compared to collections in 1996. Eggs of Uncinaria spp. were found in rectal feces (collected in late September and early October) of none of 35 (0%) live fur seal pups and 41 of 48 (85%) live sea lion pups. Packed cell volume values, determined for most of the same live pups, were essentially normal for C. ursinus but were much lower than normal for most Z. californianus. Hookworm larvae were not found in blubber of fur seal and sea lion pups or in rookery sand in July. Rookery sand, positive for live hookworm larvae when put in a refrigerator, was negative at removal 2.5 years later. The average number of eggs in utero of female hookworms was 285 for three specimens from a fur seal pup and 281 from three specimens from a sea lion pup. One hookworm larva was recovered from milk stripped from the teats of a stranded Z. californianus female at The Marine Mammal Center, Sausalito, CA.

Molecular and morphometric evidence for separate species of Uncinaria (Nematoda: Ancylostomatidae) in California sea lions and northern fur seals: hypothesis testing supplants verification.

California sea lions (Zalophus californianus) and northern fur seals (Callorhinus ursinus) are each believed to host distinct hookworm species (Uncinaria spp.). However, a recent morphometric analysis suggested that a single species parasitizes multiple pinniped hosts, and that the observed differences are host-induced. To explore the systematics of these hookworms and test these competing hypotheses, we obtained nucleotide sequences of nuclear ribosomal DNA (D2/D3 28S, D18/D19 28S, and internal transcribed spacer [ITS] regions) from 20 individual hookworms parasitizing California sea lion and northern fur seal pups where their breeding grounds are sympatric. Five individuals from an allopatric population of California sea lions were also sampled for ITS-1 and D18/D19 28S sequences. The 28S D2/D3 sequences showed no diagnostic differences among hookworms sampled from individual sea lions and fur seals, whereas the 28S D18/D19 sequences had one derived (apomorphic) character demarcating hookworms from northern fur seals. ITS sequences were variable for 7 characters, with 4 derived (apomorphic) states in ITS-1 demarcating hookworms from California sea lions. Multivariate analysis of morphometric data also revealed significant differences between nematodes representing these 2 host-associated lineages. These results indicate that these hookworms represent 2 species that are not distributed indiscriminately between these host species, but instead exhibit host fidelity, evolving independently with each respective host species. This evolutionary approach to analyzing sequence data for species delimitation is contrasted with similarity-based methods that have been applied to numerous diagnostic studies of nematode parasites.

Comparative biology of Uncinaria spp. in the California sea lion (Zalophus californianus) and the northern fur seal (Callorhinus ursinus) in California.

Studies on several aspects of the life cycle of hookworms (Uncinaria spp.) in the California sea lion (Zalophus californianus) and northern fur seal (Callorhinus ursinus) were conducted on material collected on San Miguel Island (SMI), California and at The Marine Mammal Center, Sausalito, California in 1997, 1998, and 1999. Examination of Z. californianus intestines for adult hookworms and feces for eggs revealed that longevity of these parasites in pups is about 6-8 mo, and infections are probably not present in older sea lions. Parasitic third-stage larvae (L3) were recovered from the ventral abdominal tissue of Z. californianus, suggesting transmammary transmission. Callorhinus ursinus pups had no hookworm eggs in their feces or adult worms (except for 1 probable contaminant) in their intestines in the fall and early winter, revealing that adult Uncinaria spp. are spontaneously lost at <3 mo of age of the pups. Sand samples from rookeries, used by both Z. californianus and C. ursinus, on SMI were negative for free-living, L3 in summer months but positive in fall and winter months, indicating seasonality occurred.

Uncinariasis in northern fur seal and California sea lion pups from California.

Northern fur seal (Callorhinus ursinus) (n = 25) and California sea lion (Zalophus californianus) (n = 53) pups, found dead on rookeries on San Miguel Island (California, USA), were examined for adult Uncinaria spp. Prevalence of these nematodes was 96% in fur seal pups and 100% in sea lion pups. Mean intensity of Uncinaria spp. per infected pup was 643 in fur seals and 1,284 in sea lions. Eggs of Uncinaria spp. from dead sea lion pups underwent embryonation in an incubator; development to the free-living third stage larva occurred within the egg. This study provided some specific information on hookworm infections in northern fur seal and California sea lion pups on San Miguel Island. High prevalence rate of Uncinaria spp. in both species of pinnipeds was documented and much higher numbers (2X) of hookworms were present in sea lion than fur seal pups.