Susceptibility of Raccoons (Procyon lotor) to Infection with Mycobacterium bovis

Tuberculosis due to Mycobacterium bovis infection is endemic in white-tailed deer (Odocoileus virginianus) in the northeastern portion of the lower Michigan peninsula (USA). Various wild carnivores and omnivores, including raccoons (Procyon lotor), are infected with M. bovis within the endemic area. To investigate the pathogenesis of tuberculosis in raccoons and the likelihood of M. bovis transmission from infected raccoons to other susceptible hosts, we experimentally inoculated raccoons with single oral doses of M. bovis (ranging from 30 to 1.7 x 105 colony forming units [CFU]), five daily oral doses of M. bovis (ranging from 10 to 1 x 105 CFU), or a single intravenous (IV) dose of 1 x 105 CFU of M. bovis, from November 1998 through December 2000. Granulomatous lesions consistent with tuberculosis, or tissue colonization with M. bovis, were seen in one of five raccoons in the single low oral dose group, one of five raccoons in the multiple low oral dose group, two of five raccoons in the multiple medium oral dose group, five of five raccoons in the multiple high oral dose group, and five of five raccoons in the IV inoculated group. In orally inoculated raccoons, lesions were most common in the tracheobronchial and mesenteric lymph nodes and lung. Excretion of M. bovis in saliva or nasal secretions was noted in all IV inoculated raccoons and two of five multiple low oral dose raccoons. Mycobacterium bovis was not isolated from urine or feces from any experimentally inoculated raccoons. The need for multiple large oral doses to establish infection, and the low number of orally inoculated raccoons that excreted M. bovis in nasal secretions or saliva, suggest that widespread tuberculosis among raccoons is unlikely.

Experimental Deer-To-Deer Transmission of Mycobacterium bovis

Objective—To determine whether Mycobacterium bovis can be transmitted from experimentally infected deer to uninfected in-contact deer. Animals—Twenty-three 6-month-old white-tailed deer. Procedure—On day 0, M bovis (2 X 108 colony-forming units) was administered by intratonsillar instillation to 8 deer; 3 control deer received saline (0.9% NaCl) solution. Eight in-contact deer were comingled with inoculated deer from day 21. On day 120, inoculated deer were euthanatized and necropsied. On day 180, 4 in-contact deer were euthanatized, and 4 new incontact deer were introduced. On day 360, all in-contact deer were euthanatized. Rectal, oral, and nasal swab specimens and samples of hay, pelleted feed, water, and feces were collected for bacteriologic culture. Tissue specimens were also collected at necropsy for bacteriologic culture and histologic analysis. Results—On day 90, inoculated and in-contact deer developed delayed-type hypersensitivity (DTH) reactions to purified protein derivative of M bovis. Similarly, new in-contact deer developed DTH reactions by 100 days of contact with original in-contact deer. Tuberculous lesions in in-contact deer were most commonly detected in lungs and tracheobronchial and medial retropharyngeal lymph nodes. Mycobacterium bovis was isolated from nasal secretions and saliva from inoculated and in-contact deer, urine and feces from in-contact deer, and hay and pelleted feed. Conclusions and Clinical Relevance—Mycobacterium bovis is efficiently transmitted from experimentally infected deer to uninfected in-contact deer through nasal secretions, saliva, or contaminated feed. Wildlife management practices that result in unnatural gatherings of deer may enhance both direct and indirect transmission of M bovis.

Risk of Disease from Wildlife Reservoirs: Badgers, Cattle, and Bovine Tuberculosis

Livestock face complex foraging options associated with optimizing nutrient intake while being able to avoid areas posing risk of parasites or disease. Areas of tall nutrient-rich swards around fecal deposits may be attractive for grazing, but might incur fitness costs from parasites. We use the example of dairy cattle and the risks of tuberculosis transmission posed to them by pastures contaminated with badger excreta to examine this trade-off. A risk may be posed either by aerosolized inhalation through investigation or by ingestion via grazing contaminated swards. We quantified the levels of investigation and grazing of 150 dairy cows at badger latrines (accumulations of feces and urine) and crossing points (urination-only sites). Grazing behavior was compared between strip-grazed and rotation-grazed fields. Strip grazing had fields subdivided for grazing periods of <24 h, whereas rotational grazing involved access to whole fields for 1 to 7 d each. A higher proportion of the herd investigated badger latrines than crossing points or controls. Cattle initially avoided swards around badger latrines but not around crossing points. Avoidance periods were shorter in strip- compared with rotation-grazing systems. In rotation-grazing management, latrines were avoided for longer times, but there were more investigative contacts than with strip-grazing management. If investigation is a major route of tuberculosis transmission, the risk to cattle is greatest in extensive rotation-grazing systems. However, if ingestion of fresh urine is the primary method of transmission, strip-grazing management may pose a greater threat. Farming systems affect the level and type of contact between livestock and wildlife excreta and thus the risks of disease.

SCWDS Briefs: Volume 25, Number 3 (October 2009)

Table of Contents: Clams & AI Virus SCWDS Funded to Study WNS USDA Program Changes Proposed TB in Captive Cervids CWD Prions in Deer Feces TWS Position Statement on Lead WDA Awards For SCWDS Staff New Brochure for Hog Hunters

Experimental Bolbophorus damnificus (Digenea: Bolbophoridae) Infections in Piscivorous Birds

In order to determine potential definitive hosts of the digenetic trematode, Bolbophorus damnificus, two American White Pelicans (Pelecanus erythrorhynchos), two Double-crested Cormorants (Phalacrocorax auritus), two Great Blue Herons (Ardea herodias), and two Great Egrets (Ardea alba) were captured, treated with praziquantel, and fed channel catfish (Ictalurus punctatus) infected with B. damnificus metacercariae. Patent infections of B. damnificus, which developed in both American White Pelicans at 3 days post-infection, were confirmed by the presence of trematode ova in the feces. Mature B. damnificus trematodes were recovered from the intestines of both pelicans at 21 days post-infection, further confirming the establishment of infection. No evidence of B. damnificus infections was observed in the other bird species studied. This study provides further evidence that Double-crested Cormorants, Great Blue Herons, and Great Egrets do not serve as definitive hosts for B. damnificus.

Experimental Inoculation of Coyotes with Mycobacterium bovis Susceptibility and Shedding

Several wildlife species have tested positive for bovine tuberculosis in Michigan and may potentially transmit the disease to other animals. Coyotes have the highest known prevalence in the endemic area and thus, our objective was to investigate the shedding of Mycobacterium bovis by coyotes. Four coyotes were orally inoculated with 1 ml of 1 x 105 CFU/ml of M. bovis. Oral and nasal swabs, and feces were collected regularly and tested by culture. Fecal samples were also tested by exposing guinea pigs to the coyotes' feces. All animals were necropsied to determine if infection occurred. All swabs, feces and tissues were negative on culture. The dosage of M. bovis given to these coyotes was considered biologically relevant, but was insufficient for causing infection. Due to the lack of infection, we still do not know the risk coyotes pose for shedding M. bovis.

Potential Attractants for Detecting and Removing Invading Gambian Giant Pouched Rats (Cricetomys gambianus)

BACKGROUND: Native to Africa, Gambian giant pouched rats (Gambian rats; Cricetomys gambianus Waterh.) are a threatening invasive species on a Florida island, Grassy Key. Gambian giant pouched rats shifted from a domestic pet to invading species after suspected release from a pet breeder. Because of the large size of Gambian rats (weighing up to 2.8 kg), they pose a serious threat to native species (particularly nesting species) and agricultural crops, especially if Gambian rats invade mainland Florida. Also, Gambian rats pose a threat from disease, as they were implicated in a monkeypox outbreak in the mid-western United States in 2003. The United States Department of Agriculture’s Wildlife Services has initiated eradication and detection efforts in the Florida Keys, but trapping the sparse population of Gambian rats has proven difficult. RESULTS: Fifteen attractants that could be used in traps for capturing or detecting single or paired Gambian rats were tested. It was found that conspecific scents (i.e. feces and urine) from other Gambian rats were the best treatment for attracting single and paired Gambian rats. Single Gambian rats explored more attractant types than paired Gambian rats. CONCLUSIONS: Effective attractants for use with Gambian rats have been identified, and multiple attractant types should be used to capture or detect the sparse population. It is recommended that mainly urine and feces from Gambian rats be used, but peanut butter, anise, ginger and fatty acid scent could also be useful for attracting the currently small population of Gambian rats on Grassy Key.

Cystic Echinococcosis in the Arctic and Sub-Arctic

The northern biotype of Echinococcus granulosus occurs throughout the holarctic zones of tundra and taiga, from eastern Fennoscandia to the Bering Strait in Eurasia and in North America from arctic Alaska approximately to the northern border of the United States. The cycle of the cestode is complex in taiga at lower latitudes, because of the greater diversity of potential hosts. In the Arctic and Subarctic, however, four patterns of predator/prey relationships may be discerned. Two natural cycles involve the wolf and wild reindeer and the wolf and elk (moose), respectively. Where deer of the two species coexist, both are prey of the wolf; the interactions of the wolf and elk are here described on the basis of long-term observations made on Isle Royale (in Lake Superior near the southern limit of taiga), where only the wolf and elk serve as hosts for E. granulosus. A synanthropic cycle involving herding-dogs and domesticated reindeer caused hyperendemicity of cystic echinococcosis in arctic Eurasia, mainly in northeastern Siberia. The 4th pattern, a semi-synanthropic cycle, formerly existed in Alaska, wherein sled-dogs of the indigenous hunters became infected by consuming the lungs of wild reindeer. The sequence of changes in life-style inherent in the process of acculturation affected the occurrence of cystic echinococcosis among nomadic Iñupiat in arctic Alaska. When those people became sedentary, the environs of their early villages soon became severely contaminated by feces of dogs, and cases of cystic echinococcosis occurred. Compared to cystic echinococcosis caused by E. granulosus adapted to synanthropic hosts (dog and domestic ungulates), the infection produced by the northern biotype is relatively benign. 0fearly all diagnosed cases of cystic echinococcosis (> 300 in Alaska have occurred in indigenous people; only one fatality has been recorded (in a non-indigenous person). After sled-dogs were replaced by machines, cases have become rare in Alaska. A similar effect has been observed in Fennoscandia, in the Saami and domesticated reindeer. Recent records indicate tbat the prcvalence of cystic echinococcosis is increasing in Russia, suggesting that dogs are used there in herding.

Scraping Behavior in Male White-tailed Deer as a Potential Means of Transmitting Chronic Wasting Disease

Chronic wasting disease (CWD) has become a concern for wildlife managers and hunters across the United States. High prevalence of chronic wasting disease (CWD) in older male white-tailed deer (Odocoileus virginianus) suggests that sex-specific social behavior may contribute to the spread of the disease among males. Scraping is a marking behavior performed by male white-tailed deer during the rut in which a pawed depression and associated over-hanging branch are marked with saliva, glandular secretions, urine, and feces. We placed 71 and 35 motion-activated cameras on scrapes in DeSoto National Wildlife Refuge in western Nebraska and eastern Iowa from Oct. – Nov. 2005 and Sept. – Nov. 2006, respectively. We recorded 5009 encounters and 1830 direct interactions. We developed an ethogram of behaviors of interest at scrapes. We found that males interacted with scrapes more frequently than females (P < 0.001). Male interactions were more complex, with 69% consisting of ≥2 observed behaviors versus 25% and 13% for females and fawns. We identified individual male deer ≥2.5 years old and determined the minimum number of different scrapes individuals visited and the number of individuals that visit a single scrape. Individuals that appeared on camera ≥5 times visited a mean of 3.9 scrapes (range = 1-15) and traveled a mean minimum distance of 978 m between consecutive scrapes. A mean of 5.1 individuals visited a single scrape, and up to 43% of individuals returned to a scrape previously visited at least once. We modeled Risk Values based on frequency of occurrence, duration, and Threat Values of each behavior, for contacting and transmitting CWD prions at scrapes. Adult males had the highest total Risk Values for contacting CWD prions (114.1) and shedding prions (59.4). The “grasp-lick branch” behavior had the highest Risk Value for adult males for both contacting and transmitting prions. Our study reveals a sex specific social behavior in male white-tailed deer that has the potential to spread chronic wasting disease between adult males in the population.