David A. Jessup

Coastal freshwater runoff is a risk factor for Toxoplasma gondii infection of southern sea otters (Enhydra lutris nereis)

The association among anthropogenic environmental disturbance, pathogen pollution and the emergence of infectious diseases in wildlife has been postulated, but not always well supported by epidemiologic data. Specific evidence of coastal contamination of the marine ecosystem with the zoonotic protozoan parasite, Toxoplasma gondii, and extensive infection of southern sea otters (Enhydra lutris nereis) along the California coast was documented by this study. To investigate the extent of exposure and factors contributing to the apparent emergence of T. gondii in southern sea otters, we compiled environmental, demographic and serological data from 223 live and dead sea otters examined between 1997 and 2001. The T. gondii seroprevalence was 42% (49/116) for live otters, and 62% (66/107) for dead otters. Demographic and environmental data were examined for associations with T. gondii seropositivity, with the ultimate goal of identifying spatial clusters and demographic and environmental risk factors for T. gondii infection. Spatial analysis revealed clusters of T. gondii-seropositive sea otters at two locations along the coast, and one site with lower than expected T. gondii seroprevalence. Risk factors that were positively associated with T. gondii seropositivity in logistic regression analysis included male gender, older age and otters sampled from the Morro Bay region of California. Most importantly, otters sampled near areas of maximal freshwater runoff were approximately three times more likely to be seropositive to T. gondii than otters sampled in areas of low flow. No association was found between seropositivity to T. gondii and human population density or exposure to sewage. This study provides evidence implicating land-based surface runoff as a source of T. gondii infection for marine mammals, specifically sea otters, and provides a convincing illustration of pathogen pollution in the marine ecosystem.

Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters

“Super-blooms” of cyanobacteria that produce potent and environmentally persistent biotoxins (microcystins) are an emerging global health issue in freshwater habitats. Monitoring of the marine environment for secondary impacts has been minimal, although microcystin-contaminated freshwater is known to be entering marine ecosystems. Here we confirm deaths of marine mammals from microcystin intoxication and provide evidence implicating land-sea flow with trophic transfer through marine invertebrates as the most likely route of exposure. This hypothesis was evaluated through environmental detection of potential freshwater and marine microcystin sources, sea otter necropsy with biochemical analysis of tissues and evaluation of bioaccumulation of freshwater microcystins by marine invertebrates. Ocean discharge of freshwater microcystins was confirmed for three nutrient-impaired rivers flowing into the Monterey Bay National Marine Sanctuary, and microcystin concentrations up to 2,900 ppm (2.9 million ppb) were detected in a freshwater lake and downstream tributaries to within 1 km of the ocean. Deaths of 21 southern sea otters, a federally listed threatened species, were linked to microcystin intoxication. Finally, farmed and free-living marine clams, mussels and oysters of species that are often consumed by sea otters and humans exhibited significant biomagnification (to 107 times ambient water levels) and slow depuration of freshwater cyanotoxins, suggesting a potentially serious environmental and public health threat that extends from the lowest trophic levels of nutrient-impaired freshwater habitat to apex marine predators. Microcystin-poisoned sea otters were commonly recovered near river mouths and harbors and contaminated marine bivalves were implicated as the most likely source of this potent hepatotoxin for wild otters. This is the first report of deaths of marine mammals due to cyanotoxins and confirms the existence of a novel class of marine “harmful algal bloom” in the Pacific coastal environment; that of hepatotoxic shellfish poisoning (HSP), suggesting that animals and humans are at risk from microcystin poisoning when consuming shellfish harvested at the land-sea interface.

PATTERNS OF MORTALITY IN SOUTHERN SEA OTTERS (ENHYDRA LUTRIS NEREIS) FROM 1998–2001

Detailed postmortem examination of southern sea otters (Enhydra lutris nereis) found along the California (USA) coast has provided an exceptional opportunity to understand factors influencing survival in this threatened marine mammal species. In order to evaluate recent trends in causes of mortality, the demographic and geographic distribution of causes of death in freshly deceased beachcast sea otters necropsied from 1998–2001 were evaluated. Protozoal encephalitis, acanthocephalan-related disease, shark attack, and cardiac disease were identified as common causes of death in sea otters examined. While infection with acanthocephalan parasites was more likely to cause death in juvenile otters, Toxoplasma gondii encephalitis, shark attack, and cardiac disease were more common in prime-aged adult otters. Cardiac disease is a newly recognized cause of mortality in sea otters and T. gondii encephalitis was significantly associated with this condition. Otters with fatal shark bites were over three times more likely to have pre-existing T. gondii encephalitis suggesting that shark attack, which is a long-recognized source of mortality in otters, may be coupled with a recently recognized disease in otters. Spatial clusters of cause-specific mortality were detected for T. gondii encephalitis (in Estero Bay), acanthocephalan peritonitis (in southern Monterey Bay), and shark attack (from Santa Cruz to Point Año Nuevo). Diseases caused by parasites, bacteria, or fungi and diseases without a specified etiology were the primary cause of death in 63.8% of otters examined. Parasitic disease alone caused death in 38.1% of otters examined. This pattern of mortality, observed predominantly in juvenile and prime-aged adult southern sea otters, has negative implications for the overall health and recovery of this population.

Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: New linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters

Sea otters in California are commonly infected with Toxoplasma gondii. A unique Type X strain is responsible for 72% of otter infections, but its prevalence in terrestrial animals and marine invertebrates inhabiting the same area was unknown. Between 2000 and 2005, 45 terrestrial carnivores (lions, bobcats, domestic cats and foxes) and 1396 invertebrates (mussels, clams and worms) were screened for T. gondii using PCR and DNA sequencing to determine the phylogeographic distribution of T. gondii archetypal I, II, III and Type X genotypes. Marine bivalves have been shown to concentrate T. gondii oocysts in the laboratory, but a comprehensive survey of wild invertebrates has not been reported. A California mussel from an estuary draining into Monterey Bay was confirmed positive for Type X T. gondii by multilocus PCR and DNA sequencing at the B1 and SAG1 loci. This mussel was collected from nearshore marine waters just after the first significant rainfall event in the fall of 2002. Of 45 carnivores tested at the B1, SAG1, and GRA6 typing loci, 15 had PCR-confirmed T. gondii infection; 11 possessed alleles consistent with infection by archetypal Type I, II or III strains and 4 possessed alleles consistent with Type X T. gondii infection. No non-canonical alleles were identified. The four T. gondii strains with Type X alleles were identified from two mountain lions, a bobcat and a fox residing in coastal watersheds adjacent to sea otter habitat near Monterey Bay and Estero Bay. Confirmation of Type X T. gondii in coastal-dwelling felids, canids, a marine bivalve and nearshore-dwelling sea otters supports the hypotheses that feline faecal contamination is flowing from land to sea through surface runoff, and that otters can be infected with T. gondii via consumption of filter-feeding marine invertebrates.

Mass Stranding of Marine Birds Caused by a Surfactant-Producing Red Tide

In November-December 2007 a widespread seabird mortality event occurred in Monterey Bay, California, USA, coincident with a massive red tide caused by the dinoflagellate Akashiwo sanguinea. Affected birds had a slimy yellow-green material on their feathers, which were saturated with water, and they were severely hypothermic. We determined that foam containing surfactant-like proteins, derived from organic matter of the red tide, coated their feathers and neutralized natural water repellency and insulation. No evidence of exposure to petroleum or other oils or biotoxins were found. This is the first documented case of its kind, but previous similar events may have gone undetected. The frequency and amplitude of red tides have increased in Monterey Bay since 2004, suggesting that impacts on wintering marine birds may continue or increase.

Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system.

The processes promoting disease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when disease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern sea otter (Enhydra lutris nereis) population growth: disease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged sea otters and evaluated infection with 2 disease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where otters had high levels of infection with T. gondii. We found that otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in sea otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and disease working synergistically to limit recovery.

Effects of capture on biological parameters in free-ranging bighorn sheep (Ovis canadensis): evaluation of normal, stressed and mortality outcomes and documentation of postcapture survival.

Blood samples and physiological data were collected from 634 bighorn sheep (Ovis canadensis) captured by four different methods between 1980 and 1986 in the western United States. These parameters were evaluated for selected physiological, biochemical and hematological values. Postcapture biological parameters were compared among bighorn sheep according to four different outcomes; normal, stressed or compromised, capture myopathy (CM) mortality, and accidental mortality. Significant differences (P < 0.05) were noted between outcome groups relative to certain parameters: temperature, respiration, creatinine phosphokinase (CPK), lactic dehydrogenase (LDH), serum glutamic oxaloacetic transaminase (SGOT), blood urea nitrogen (BUN), glucose, white blood cell count (WBC) and plasma pH. Such differences between groups may help in evaluating the clinical status of bighorn sheep at capture, enabling one to predict those animals that might develop CM at a later date, indicate candidates for preventive medical treatment prior to release, and/or which should be followed closely to determine long-term survival. Evaluation of follow-up data (n = 77) related to outcome status and long-term survival of bighorn sheep indicated that <4% (3 of 77) were dead within 1 mo of capture (one of these had been classified as normal and two as stressed or compromised at capture); <3% (3 of 77) were dead >1 mo, and <6 mo after capture two were classified in the stressed outcome and one as diseased. Eighty-eight percent (68 of 77) were alive from 1 mo to 5 yr after capture (53 were classified as normal, 12 as stressed or compromised and 3 as diseased), and 2% (1 of 77) had chronic CM but was still alive (this animal had been classified as normal). Of 77 sheep in the follow-up group, <3% (2 of 77) were not observed following capture (one was classified as normal and one as stressed and diseased). Of the fatalities, <3% (2 of 40) had been captured by the net-gun and <4% (1 of 27) by drive-net. Those two unobserved in the follow-up group also had been caught with the net-gun, 5% (2 of 40). The single surviving CM case had been captured by the net-gun. Although the net-gun appears to be one of the safest methods of capturing individual bighorn sheep, based on evaluation of capture data and biological parameters, it may not be associated with the best long-term survival in some bighorn sheep. This further emphasizes the need for close monitoring of animals at capture and following their release.

CAPTURE METHODS IN FIVE SUBSPECIES OF FREE-RANGING BIGHORN SHEEP: AN EVALUATION OF DROP-NET, DRIVE-NET, CHEMICAL IMMOBILIZATION AND THE NET-GUN

Six hundred thirty-four bighorn sheep (Ovis canadensis) were captured in the western United States between 1980 and 1986, using four different methods: drop-net (n = 158), drive-net (n = 249), chemical immobilization (n =90) and net-gun (n =137). The net-gun was found to have considerable advantages over the use of ground nets and chemical immobilization methods for capturing bighorn sheep. Evaluation of specific outcome categories for individual sheep, including normal, compromised (stress-induced), mortality from capture myopathy (CM), and accidental mortality, revealed significant differences in these rates between capture groups (P < 0.05). The use of the net-gun resulted in the lowest proportion of compromised sheep at 11% (15/137), had no CM mortality, and resulted in a 2% (2/137) accidental mortality. The use of drop-nets resulted in 15% compromised sheep (24/158), a CM mortality rate of 2% (3/158), and an accidental mortality rate of 1% (2/158). A similar proportion of sheep were compromised with the drive-nets (16%, 39/249). This method also had the highest CM mortality rate at 3% (7/249), and an accidental mortality rate of <1% (2/249). Chemical immobilization resulted in the most compromised sheep at 19% (17/90), had a CM mortality rate of 2% (2/90), and caused the most accidental deaths at 6% (5/90). Drop-nets and drive-nets were comparable when combining total mortality with rates for compromised bighorn sheep, 18% and 19%, respectively (29/158 and 48/249). Chemical immobilization had the highest combined measure of risk at 27% (24/90) and net-gun lowest at 12% (17/137). Advantages of the net-gun, which might account for the lower rates, include rapid and accurate deployment which results in short capture and processing times. The net-gun is highly effective in the capture of individual and occasionally pairs of sheep. Large groups of bighorn sheep can be most effectively captured, with apparently minimal compromise, using ground nets. Chemical immobilization, unless all other alternatives are considered inappropriate, cannot be recommended.

EFFECTS OF CAPTURE ON BIOLOGICAL PARAMETERS IN FREE-RANGING BIGHORN SHEEP (OVIS CANADENSIS): EVALUATION OF DROP-NET, DRIVE-NET, CHEMICAL IMMOBILIZATION AND THE NET-GUN

Blood samples and physiological data were collected from 634 bighorn sheep captured between 1980 and 1986 in the western United States. Bighorn sheep were evaluated for physiological parameters (temperature, pulse and respiration), selected biochemical parameters (Cortisol, creatine phosphokinase (CPK), serum glutamic oxaloacetic transaminase (SGOT), lactic dehydrogenase (LDH), alkaline phosphotase (AP), potassium, sodium, chloride, creatinine, blood urea nitrogen (BUN), selenium, glucose, total protein, plasma pH and plasma PCO2), and selected hematological parameters (packed cell volume (PCV), hemoglobin (HB), red blood cell count (RBC), and white blood cell count (WBC)). These parameters were compared among bighorn sheep captured by four different methods: drop-net (n = 158), drive-net (n = 249), chemical immobilization (n =90) and the net-gun (n = 137). Biological parameters affected by stress, including temperature, respiration, Cortisol, CPK, SGOT, potassium, glucose and WBC revealed significant differences among capture methods (P < 0.05). Some blood parameter differences, including temperature, respiration, Cortisol, glucose and WBC could be explained partially by the distribution of age and sex within capture method groups. Drop-net and net-gun methods of capture appeared to produce the least amount of alteration to biological parameters related to capture stress or compromise and capture mortality. Drive-net was similar to the former methods while chemical immobilization caused the greatest changes in the above physiological, biochemical and hematological parameters.

Anaesthetic and Sedative Techniques for Aquatic Animals. 3rd Edition

Professor Ross began Anaesthetic and Sedative Techniques for Aquatic Animals with a set of course notes developed in 1983 and, later, expanded and heavily referenced his work in a second edition published by Blackwell about 10 yr ago. In this third edition, Lindsay G. Ross—with his wife, Barbara Ross, and daughter, Bryony Ross—has further expanded and updated the material, covering a field that has grown increasingly controversial and challenging within the last decade. It has taken some time—years in fact—for the fish-and-wildlife–management and scientific communities to accept the fact that sedation and anesthesia (American-English spelling will be used in this review) of fish, invertebrates, amphibians, and reptiles is not only humane and good practice, but also desirable, and that some techniques are applicable to larger-scale operations such as hatcheries. On the down side, the resources required for many advances made in aquatic animal anesthesia are not yet widely available, or the procedures are prohibited due to food-safety concerns on food fish, but more on this later. The authors note that this book is the ‘‘only substantial reference work on fish anaesthesia,’’ and although this is perhaps true as stated, it is not the only source of information on the subject, given that several current large works on fish medicine and care contain good chapters on anesthesia. Anaesthetic and Sedative Techniques for Aquatic Animals, however, is substantive, with 15 chapters including the following: ‘‘Defining Stress in Aquatic Animals’’; ‘‘Pain in Aquatic Animals’’; ‘‘The Nature of Anaesthesia, Sedation and Analgesia’’; ‘‘The Features of Anaesthetic Agents’’; ‘‘Anaesthesia and Legislation’’; ‘‘Factors Affecting the Response of Aquatic Ectotherms to Anaesthesia’’; ‘‘Anaesthesia of Fish I: Inhalation Anaesthesia’’; ‘‘Anaesthesia of Fish II: Inhalation Anaesthesia Using Gases’’; ‘‘Anaesthesia of Fish III: Parenteral and Oral Anaesthesia’’; ‘‘Anaesthesia of Fish IV: Nonchemical Methods’’; ‘‘Anaesthesia of Aquatic Invertebrates’’; ‘‘Anaesthesia of Amphibians and Reptiles’’; ‘‘Transportation and Anaesthesia’’; and ‘‘Concluding Remarks.’’ If you have missed all the sound and fury in the last decade or two over whether ‘‘fish feel pain,’’ whether and how they manifest stress, and the effects of pain and stress on fish health, along with numerous other issues, you might wonder about the need for several of the first six or seven chapters. As a veteran and survivor of these controversies, Dr Ross lays a pretty solid base for the fact that fish do indeed feel pain (or at least noxious stimuli that cause avoidance) and that aquatic animal anesthesia and sedation is not just for the weak-at-heart. The authors write: ‘‘Indeed, because these specific receptors (nociceptors) and their axons can be readily identified in invertebrates, they have been widely used as models in neurophysiological research for many years.’’ Although ‘‘fish feel pain’’ may seem like common sense and is now pretty widely accepted, the citations supporting this were relatively few and old, which I find a disturbing oversight. This is probably an area where newer citations should have been added to bolster classical papers on the subject. On the subject of stress, the following quote seemed somewhat overstated: ‘‘The response to these hormones is fairly consistent and, although their release adapts an animal to respond to an environmental change, there is Journal of Wildlife Diseases, 45(2), 2009, pp. 552–554