Case Report: Subclinical Verminous Pneumonia and High Ambient Temperatures Had Severe Impact on the Anesthesia of Semi-domesticated Eurasian Tundra Reindeer (Rangifer tarandus tarandus) With Medetomidine–Ketamine

Semidomesticated Eurasian tundra reindeer (Rangifer tarandus tarandus, n = 21) were scheduled twice for chemical immobilization with medetomidine–ketamine as part of a scientific experiment in June 2014. During the first round of immobilizations, seven animals developed severe respiratory depression (RD). Three individuals died, and 4 recovered. The ambient temperature during the 2 days of immobilization (June 3 and 4) was high (mean 13.9–17.6°C) compared to the normal mean temperature for these 2 days (7–8°C) based on statistical records. During the second round of immobilizations, using the same anesthetic protocol for the remaining animals as in the first round but conducted under cooler conditions (mean 6.6°C for the period June 9–18), no signs of RD were observed. Clinical and pathological investigations indicated that the animals suffered from circulatory changes possibly caused by high ambient temperatures and granulomatous interstitial pneumonia due to Elaphostrongylus rangiferi larvae. These conditions, together with the cardiovascular effects of medetomidine, were likely causes of RD and the fatal outcome. We conclude that chemical immobilization of reindeer with medetomidine–ketamine should be avoided in May–June due to the potential risk when animals partly in winter coats encounter rising ambient temperatures and usually have parasites developing in their airways.

Modeling Thermal Suitability for Reindeer (Rangifer tarandus ssp.) Brainworm (Elaphostrongylus rangiferi) Transmission in Fennoscandia

The brainworm, Elaphostrongylus rangiferi, is a nematode which causes neurological disorders (elaphostrongylosis) in reindeer (Rangifer tarandus ssp.). Favorable climatic conditions have been inferred as the cause of sporadic outbreaks of elaphostrongylosis in Norway, supported by positive associations between observed outbreaks/intensity of infection and summer temperatures in the previous years. Climate warming which results in increased transmission of E. rangiferi therefore presents a risk to the health of semi-domesticated and wild reindeer in Fennoscandia (Norway, Sweden, and Finland), the health of co-grazing small ruminants, and the livelihoods of indigenous Sámi herders. As a first step toward developing climate change impact assessments for E. rangiferi, a degree-day model was developed for larval development in a range of gastropod hosts and applied to historic weather data. Predictions were validated by statistical and qualitative comparison against historic parasitological and outbreak records. The model predicted an overall increase in thermal suitability for E. rangiferi, which was statistically significant in the north and along the Scandinavian mountain ranges, where reindeer density is highest. In these regions annual cumulative temperature conditions are suitable for larval development within a single year, potentially changing E. rangiferi epidemiology from a 2-year transmission cycle to a 1-year transmission cycle. This is the first mechanistic model developed for E. rangiferi and could be used to inform veterinary risk assessments on a broad spatial scale. Limitations and further developments are discussed.

HELMINTOFAUNA OF THE YOUNG REINDEER (RANGIFER TARANDUS) IN THE LENINGRAD REGION

Reindeer (Rangifer tarandus) traditionally inhabit the circumpolar territories. However, in recent years, about ten reindeer farms have been created in the Leningrad Region, in which imported animals began to breed. Freshly excreted feces of calves were collected in the ethnic park Lesnaya Izbushka and in the zoo Shishki Na Lampushke in the summer of 2019 and on the day of sampling they were delivered to the Laboratory for the Study of Parasitic Diseases at the Department of Parasitology of the St. Petersburg State Academy of Veterinary Medicine. Ovoscopy was performed according to the Darling`s technique and sequential washes, larvoscopy was performed according to the Wajda`s technique, and helminthoscopy was performed by macroscopic examination of feces. Nematodes were found in young reindeer from the Lesnaya Izbushka ethnic park: Strongylida (eggs), Capillaria sp. (eggs) and Elaphostrongylus rangiferi (larvae of the first stage). The same helminths were found in the parent herd. In a calf born in 2019 at the zoo Shishki Na Lampushke, no helminthes were found. Since parasitic worms require a certain time from the moment of invasion of the host to the beginning of reproduction, it is necessary to continue monitoring the reindeer. All helminths found in young reindeer are not dangerous to humans.

REGULAR ARTICLES / ARTICLES RÉGULIERSFactors affecting the distribution and transmission of Elaphostrongylus rangiferi (Protostrongylidae) in caribou (Rangifer tarandus caribou) of Newfoundland, Canada

Elaphostrongylus rangiferi was introduced to caribou (Rangifer tarandus caribou) of Newfoundland by infected reindeer (R. t. tarandus) from Norway and has caused at least two epizootics of cerebrospinal elaphostrongylosis (CSE), a debilitating neurologic disease. In an attempt to understand the conditions necessary for such outbreaks, we examined the effects of herd density and climatic factors on parasite abundance. The abundance of E. rangiferi was represented by counts of first-stage larvae in feces collected from young caribou (calves and yearlings) in 7 distinct caribou herds in Newfoundland. Abundance of E. rangiferi was highest in February and in the Avalon (632 ± 14 (mean ± SE)) and St. Anthony (526 ± 145) herds, the 2 herds in which CSE was most frequently reported. Mean abundance in February samples from young animals correlated positively with mean annual minimum temperature (rS = 0.829, df = 6, P = 0.04) and the number of days per year above 0°C (rS = 0.812, df = 6, P = 0.05) and negatively with mean summer temperatures (rS = –0.830, df = 6, P = 0.04). Results suggest that abundance of E. rangiferi and the likelihood of cases of CSE are increased by moderate summer temperatures suitable for the activity and infection of gastropod intermediate hosts and by mild winters with little snow that extend the transmission period. Abundance of larvae was not correlated with herd density. Animals in all 7 herds also had the muscle worm Parelaphostrongylus andersoni, a related nematode with similar dorsal-spined larvae. In 2 additional herds (Cape Shore and Bay de Verde), P. andersoni occurred alone and larvae were passed only by young caribou. In herds with dual infections, numbers of P. andersoni larvae were depressed, declined more quickly in young animals, and were considered to be present in only low numbers in February samples used for E. rangiferi analysis. Upon initial infection, young caribou develop a resistance to E. rangiferi that prevents or reduces reinfection later in life. This was demonstrated by examining the brains of caribou for recently acquired worms, which must develop there for up to 90 days before continuing their tissue migration into the skeletal muscles. Recent infections were detected in only calves and yearlings in all herds with E. rangiferi except the Avalon herd, where developing worms were also found on the brains of older caribou. The infection of older animals in the Avalon herd may reflect a lower immunocompetence of a naive herd that has only recently been exposed to E. rangiferi.

The temperature threshold for development of Elaphostrongylus rangiferi in the intermediate host: an adaptation to winter survival?

SUMMARYTo test the hypothesis that the relatively high developmental temperature threshold of the parasitic nematode Elaphostrongylus rangiferi in the intermediate snail host is an adaptation to minimize larval mortality during winter, an experiment was set up in which snails of the species Arianta arbustorum were experimentally infected with the parasite. The snails were divided into 3 groups known to contain 1st, 2nd or 3rd-stage larvae, and incubated at 3 °C for an experimental period of 18 weeks. First-stage larvae showed a significantly higher survival rate within snails than 2nd or 3rd-stage larvae. We also found that snails carrying 1st-stage larvae survived better than snails with other larval stages. It is concluded that if the nematode has started development before the hibernation, this has a real and significant effect on the risk of dying. The high developmental threshold is therefore likely to be an adaptation to reduce the chance of hibernating as developing larvae during long periods of low temperatures.

Experimental studies of Elaphostrongylus rangiferi in reindeer (Rangifer tarandus tarandus): Clinical observations

Clinical observations were made on 12 reindeer calves (Rangifer tarandus tarandus) experimentally infected with 200-1000 infective larvae of Elaphostrongylus rangiferi and autopsied 2.5-196 days post inoculation (p.i). Seven experimental animals autopsied later than 20 days p.i. all developed neurologic signs starting 4-8 weeks p.i. In six of these animals, signs lasted until autopsy 0-12 weeks after onset. The seventh animal recovered completely after a disease period lasting five months. A dose-response relationship between the infective dose and severity of signs was observed. Clinical signs observed in all affected animals were paraparesis, tail paresis and posterior ataxia. Other signs included lowered head, general weakness, lameness, tetraparesis, scoliosis, anal hypotonia, head and neck turn, depression and reduced vision. The prepa-tent period was 4-4.5 months.