Bringing Back a Healthy Buzz? Invertebrate Parasites and Reintroductions: A Case Study in Bumblebees

Reintroductions can play a key role in the conservation of endangered species. Parasites may impact reintroductions, both positively and negatively, but few case studies of how to manage parasites during reintroductions exist. Bumblebees are in decline at regional and global scales, and reintroductions can be used to re-establish extinct local populations. Here we report on how the risks associated with parasites are being managed in an ongoing reintroduction of the short-haired bumblebee, Bombus subterraneus, to the UK. Disease risk analysis was conducted and disease risk management plans constructed to design a capture-quarantine-release system that minimised the impacts on both the bumblebees and on their natural parasites. Given that bumblebee parasites are (i) generalists, (ii) geographically ubiquitous, and (iii) show evidence of local adaptation, the disease risk management plan was designed to limit the co-introduction of parasites from the source population in Sweden to the destination site in the UK. Results suggest that this process at best eliminated, or at least severely curtailed the co-introduction of parasites, and ongoing updates of the plan enabled minimization of impacts on natural host-parasite dynamics in the Swedish source population. This study suggests that methods designed for reintroductions of vertebrate species can be successfully applied to invertebrates. Future reintroductions of invertebrates where the parasite fauna is less well known should take advantage of next-generation barcoding and multiple survey years prior to the start of reintroductions, to develop comprehensive disease risk management plans.

     

Experimental Trichinella infection in seals

The susceptibility of seals to infection with Trichinella nativa and the cold tolerant characteristics of muscle larvae in seal meat were evaluated. Two grey seals, Halichoerus grypus, were inoculated with 5000 (100 larvae/kg) T. nativa larvae and two grey seals with 50000 (1000 larvae/kg). One seal from each dose group and two control seals were killed at 5 and 10 weeks post-inoculation (p.i.). At 5 weeks p.i., infection was established in both low and high dose seals with mean larval densities of 68 and 472 larvae per gram (lpg), respectively, using eight different muscles for analyses. At 10 weeks p.i., mean larval densities were 531 and 2649 lpg, respectively, suggesting an extended persistence of intestinal worms. In seals with high larval density infections, the distribution of larvae in various muscles was uniform, but in one seal with a low larval density infection, predilection sites of larvae included muscle groups with a relative high blood flow, i.e. diaphragm, intercostal and rear flipper muscles. Trichinella-specific antibody levels, as measured by ELISA, increased during the 10 week experimental period. Infected seal muscle was stored at 5, -5 and -18 degrees C for 1, 4 and 8 weeks. Muscle larvae released from stored seal muscle by artificial digestion were inoculated into mice to assess viability and infectivity. Larvae from seal muscle 10 weeks p.i. tolerated -18 degrees C for 8 weeks but larvae from seal muscle 5 weeks p.i. tolerated only 1 week at -18 degrees C, supporting the hypothesis that freeze tolerance increases with the age of the host-parasite tissue complex. The expressed susceptibility to infection, extended production of larvae, antibody response and freeze tolerance of T. nativa in seals are new findings from the first experimental Trichinella infection in any marine mammal and suggest that pinnipeds (phocids, otariiids or walrus) may acquire Trichinella infection by scavenging even small amounts of infected tissue left by hunters or predators.     

Serologic survey of Brucella spp. antibodies in some marine mammals of North America

A serologic survey of anti-Brucella spp. antibodies was undertaken on 2,470 samples of 14 North American marine mammal species collected between 1984-97. Serum or blood from eight species of cetaceans and six species of pinnipeds was sampled from Pacific, Atlantic, and Arctic oceans. Two competitive enzyme-linked immunosorbent assays (C-ELISA's), using specific monoclonal antibodies to Brucella abortus cell wall components, were used to detect anti-Brucella spp. antibodies in the samples. Sera from 33 cetaceans and 61 pinnipeds gave inhibition values, in one or both of the tests, which exceeded the threshold that indicates Brucella spp. exposure in cattle. Seropositive animals were identified from Pacific, Atlantic, and Arctic oceans. While Brucella spp. was not isolated, differences in the response of seropositive cetacean and pinniped sera in the two assays suggest that two antigenically distinct species or biovars of Brucella spp. are present. No pathology consistent with clinical brucellosis was noted in any of the animals tested although detailed examination was not conducted on all carcasses.     

A morbillivirus antibody survey of Atlantic walrus, narwhal and beluga in Canada

A longitudinal serologic survey was conducted for morbillivirus antibodies in Atlantic walruses (Odobenus rosmarus rosmarus), narwhal (Monodon monoceros), and beluga (Delphinapterus leucas) from the Northwest Territories, Nunavut and the St. Lawrence estuary (Canada). Sixty-five of 131 (50%) walruses sampled between 1984 and 1993 had detectable morbillivirus neutralizing antibodies. Positive walrus were identified from four of five Arctic sampling sites, to as far back as 1984. Prevalence of morbillivirus neutralizing antibodies in walruses from Foxe Basin ranged from a high of 76% (n = 21) in 1993 to a low of 22% (n = 28) in 1984. Limitations in sample acquisition may have produced underestimates for the 1984 data. There are no reports of clinical morbillivirus infection in walruses. Our results are consistent with the hypothesis that a morbillivirus similar or identical to phocine distemper virus (PDV) has circulated among walrus populations of the eastern Canadian Arctic, at least since the early 1980s. No narwhal (n = 79) or beluga (n = 445) from Arctic waters were identified as having antibodies to dolphin morbilivirus (DMV) above the threshold serum dilution of log2 4. Also, none of the beach-cast cetacean carcasses (n = 28) from the Gulf of St. Lawrence and the St. Lawrence estuary were positive for antibodies to DMV. This indicates that Gulf of St. Lawrence, St. Lawrence estuary, and Arctic cetaceans either have not been exposed to DMV or an antigenically related morbillivirus, or are not susceptible to infection.     

Seasonal changes in erythrocyte osmotic fragility and haematocrit in American plaice infected with Haemohormidium terranovae

American plaice held in captivity for a period of 8 months over winter exhibited increasing erythrocyte osmotic fragility and decreasing haematocrit values until December. In December, osmotic fragility parameters and haematocrit were strongly correlated, suggesting anaemia due to disruption of circulating erythrocytes. Intensity of infection with Haemohormidium terranovae increased through the winter months until March but was not correlated either with osmotic fragility or haematocrit. These results are explained in terms of compensatory haemopoetic changes occurring in plaice. Mortality was apparently unrelated to any of the parameters investigated.     

Redescription of Synthesium pontoporiae n. comb. with notes on S. tursionis and S. seymouri n. comb. (Digenea: Brachycladiidae Odhner, 1905)

Synthesium pontoporiae n. comb. is redescribed, together with Synthesium tursionis and Synthesium seymouri n. comb.; the parasites were obtained from stranded and accidentally caught cetaceans. The sucker ratio (ratio between widths of the oral and ventral suckers) in S. pontoporiae was 1:1.8-3.0 (mean 1:2.2); in S. tursionis was 1:0.8-1.2; and in S. seymouri was 1:0.5-0.7. Synthesium pontoporiae differed from its congeners by additional diagnostic characters, including: oval to lobed testes; small cirrus with pyriform proximal region and flexible, tubular distal region formed by evagination of ejaculatory duct; and vitellarium in small follicles extending from the level of the seminal vesicle to the posterior extremity of the body and not forming dendritic radial bunches. Data on the morphology of adult S. pontoporiae and S. tursionis were inferred from confocal laser microscopical observations.     

Hematology and serum chemistry of harp (Phoca groenlandica) and hooded seals (Cystophora cristata) during the breeding season, in the Gulf of St. Lawrence, Canada

Standard hematologic and serum chemistry parameters were determined from 28 harp seals (Phoca groenlandica) and 20 hooded seals (Cystophora cristata) sampled from 6 March 2001 to 13 March 2001 during the breeding season. Whole blood was collected immediately postmortem from harp seal mother-pup pairs and from six hooded seal pups, and from live-captured adult hooded seals and three hooded seal pups; blood was analyzed within 24 hr at a local human hospital. A certified veterinary laboratory validated subsamples of whole blood and analyzed all serum chemistry parameters. Significant interlaboratory differences in mean values of packed cell volume (PCV) and mean cell volume (MCV) were found. Significant differences were found between samples from the five seal groups (adult male hooded seals, lactating female hooded seals, unweaned hooded seal pups; lactating female harp seals, and unweaned harp seal pups) for hematology and most serum chemistry parameters. In general, age-class influenced mean values of PCV, hemoglobin (HB), red blood cell (RBC) counts, MCV, mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), and nucleated red blood cell (NRBC) counts per 100 leucocytes, but most age-related variations were species specific. Harp seal pups had significantly lower mean values of HB, PCV, MCH, and MCHC than did other seal groups, and significantly lower mean RBC counts than did hooded seal pups. Mean NRBC counts per 100 leukocytes were more than three times higher in harp seal pups than in hooded seal pups, but this difference was not statistically significant. Mean MCV were significantly lower in harp and hooded seal pups compared to those of adult harp and hooded seals. Differences in hemograms between pup species were likely because of the precocious development of hooded seal pups, which are weaned within 4 days, compared to 12 days for harp seal pups. Among adult seal groups, male hooded seals had significantly higher mean values of PCV and HB than did female harp and hooded seals, and significantly higher mean RBC counts than did adult female hooded seals. Among adult females, mean values of MCH and MCHC were statistically higher in hooded seals than in harp seals. Adult female harp and hooded seals did not differ significantly in other RBC parameters and mean leukocyte counts. Mean values of glucose, blood urea nitrogen, total bilirubin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein, and albumin showed species-specific variations between adults and pups. Except for ALP, few significant differences in mean enzyme activities of aspartate aminotransferase (AST), ALT, creatine kinase and gamma-glutamyltransferase were found between seal groups. Mean concentrations of electrolytes (calcium, phosphorus, sodium, potassium, chloride, magnesium, and total carbon dioxide) varied with age class, but variations in potassium and magnesium were species specific. Harp seal pups had significantly higher mean phosphorus and potassium levels compared to other seal groups.     

Bringing Back a Healthy Buzz? Invertebrate Parasites and Reintroductions: A Case Study in Bumblebees

Reintroductions can play a key role in the conservation of endangered species. Parasites may impact reintroductions, both positively and negatively, but few case studies of how to manage parasites during reintroductions exist. Bumblebees are in decline at regional and global scales, and reintroductions can be used to re-establish extinct local populations. Here we report on how the risks associated with parasites are being managed in an ongoing reintroduction of the short-haired bumblebee, Bombus subterraneus, to the UK. Disease risk analysis was conducted and disease risk management plans constructed to design a capture-quarantine-release system that minimised the impacts on both the bumblebees and on their natural parasites. Given that bumblebee parasites are (i) generalists, (ii) geographically ubiquitous, and (iii) show evidence of local adaptation, the disease risk management plan was designed to limit the co-introduction of parasites from the source population in Sweden to the destination site in the UK. Results suggest that this process at best eliminated, or at least severely curtailed the co-introduction of parasites, and ongoing updates of the plan enabled minimization of impacts on natural host-parasite dynamics in the Swedish source population. This study suggests that methods designed for reintroductions of vertebrate species can be successfully applied to invertebrates. Future reintroductions of invertebrates where the parasite fauna is less well known should take advantage of next-generation barcoding and multiple survey years prior to the start of reintroductions, to develop comprehensive disease risk management plans.