Investigation of Chronic Disease in a Captive Mara Colony

1. Investigation of Chronic Disease in a Captive Mara Colony Mexico

2. Index Case • July 21, 2001 • 2 year old captive born male mara (Dolichotispatagonum) died shortly after presenting with weakness and anorexia

3. Index Case-con’t • Animal had disseminated fungal infection affecting mostly the liver, adrenal and lymph nodes • Cytology evaluation of the lymph node, adrenal and liver revealed numerous cytoplasmic yeast-like organisms • 2-4 um in diameter • Clear halo surrounding them • In the cytoplasm of phagocytic cells and adrenocortical cells • Gomori’s methenamine silver stain positive • Histoplasma capsulatum var capsulatum was isolated from spleen

4. Case Confirmation • Gross necropsy findings • Histological findings • Other testing • Special stains • Transmission electron microscopy • Organism isolation • Exoantigen test • Immunohistochemistry

5. Establishing Endemic Levels • Intradermal testing • Common test in humans and equine • Test location on abdomen • 18/29 animals negative at 72 hours • No clinical, hematolgical, radiographic or immunologic evidence of histoplasmosis in these animals • No prior cases of histoplasmosis in this collection

6. Is There An outbreak? • There is no evidence of histoplasmosis previous to these cases in the entire collection • Is there the probability that more animals in the mara colony could have been exposed ot the disease? • Maras use dens dug in the ground, each den is used several times by different females • The intradermal testing, that is the only practical way to detect positive animals, was negative.

7. Descriptive Epidemiology • Herd history • Environmental factors

8. Herd History • Mara colony at park for >20 years • 1997: 5 animals from Argentina added to group • 1 male, 4 females • Reproduction good since introduction (66 births) • During time of the index case • Herd composed of 29 animals

9. Environmental Factors • Diet • Water ad libitum • Oranges, carrots, chopped alfalfa and rabbit pellets • Enclosure • 120m2 • Fenced with 1.20m high wire mesh and bamboo on one side • Sandy substrate • Often see squirrels (Spermophilus variegatus), Mice (Mus musculus) and various birds inside the enclosure. • Often see opossum (Didelphis virginiana), ringtail cat (Bassariscus astutus) and stray cats (Felis domesticus) inside the park. • Several wild colonies of insectivorous bats (Tadarida brasiliensis)

10. Subsequent Cases • April 25, 2002 • Died after presenting with progressive weight loss • Severe granulomatous typhlocolitis and moderate granulomatous gastrohepatic lymphadenitis • Similar organisms in the cytoplasm of macrophages

11. Case #2 • Gross necropsy findings • Thickening of the large intestinal mucosa • Watery to mucoid small intestinal contents • Histopathology • Severe, chronic grnaulomatous and fibrosing hepatitis and adrenalitis with foci of necrosuppurative inflammation • Granulomatous typhlocolitis • Adrenocortical cells had abundant similar organisms in their cytoplasm with no associated lesion • Histoplasma capsulatum var. capsulatum was isolated from the liver and adrenal gland.

12. Is This An Outbreak? • Retrospective review of 54 animals revealed no other lesions compatible with Histoplasmosis • Previously non-tested animals were tested with high-dose antigen testing • All animals negative • Investigate immune status of animals and contamination status of environment

13. Immune Status and Environment • No previous evidence of histoplasmosis in this mara colony • High probability that more animals in the colony could have been exposed to disease • Intradermal testing is the only practical way to test these animals • questionable accuracy • Immunological status of the colony would contribute to presence of disseminated histoplasmosis in more animals

14. Hypotheses • Unusual susceptibility of this species to the disease • Low immunological status of the group • Predisposing them to disease • High environmental contamination

15. Investigate Hypothesis • Review literature for similar cases • Environmental Investigation

16. Literature Review • No reports of disseminated histoplasmosis in maras or any rodent species • Report of a localized mucocutaneous histoplasmosis in a rabbit • Reports of histoplasmosis affecting the skin and lymph nodes of Badgers in Europe

17. Environmental Investigation • Environmental sampling of mara areas • No growth • Mice inoculated with extracts of environmental samples DID seroconvert • Demonstrates presence of organism in the enclosure • 2 bat colonies in the park were sampled • No culture growth • NO seroconversion in mice

18. Environmental Investigation • Climatic conditions of park does not promote the proliferation of the fungus • Sandy substrate, low humidity, lack of bird or bat droppings • But indirect evidence of fungal presence was found • Bats play an important role in fungal dissemination • Abundance of insectivorous bats in park • Other carnivorous wild animals in the park could disseminate the fungus • Serology is pending

19. Treatment and Intervention • Disinfect • Foot baths with phenolic base products • Dedicated tools to affected areas • 80cm of dirt removed from enclosure and replaced • Disinfection of holding area • Communicate to staff • Provided with masks • Review of personal hygiene • Quarantine • All maras moved to quarantine

20. Long Term • Control of immune status of the colony • Review sex ratio and demographics • Review genetics • Monitor wild bat colonies within the park

21. References • Chavez-Tapia D.B., R. Vargas-Yañes, G. Rodríguez-Arellanes, G. R. Peña-Sandoval, J. J. Flores-Estrada, M Reyes-Mo0ntes, M. L. Taylor. 1998. El murciélago como reservorio y responsable de la dispersión de Histoplasma capsulatum en la naturaleza. Rev. Inst. Nal. Enf. Resp. Mex. 11(3):187-191 • Kapustin N. Kanitz C. and Muech T. 1999. Identification of a retrovirus in Bennett`s (Macropus rufrogriseus frutica) and Dama (Tammar) (Macrophus eugenni) Wallabies. Proc. Am. As. Zoo Vet. Pp; 262 • Morita T., M. Kishimoto, A. Shimada, Y. Matsumoto and J. Shindo. 2001. Disseminated histoplasmosis in a Sea Otter (Enhydra lutris). J. Comp. Path . 125: 219-223. • Rezabek G. B., J. M. Donahue, R. C. Giles, M. B. Petrites-Murphy, K. B. Poonacha, J. R. Rooney, B, J, Smith, T. W. Swerczek and R. R. Tramontin. 1993. Histoplasmosis in Horses., J. Comp Path . 109:47-55. • Rosas-Rosas A., C. J. Salles, G. Rodríguez-Arellanes, M. L. Taylos, M. M. Garner. 2004. Disseminated Histoplasma capsulatum var. capsulatum infection in a captive mara ( Dolichotis patagonum) In Press…… • Taylor M. L., C. B. Chavez-Tapia, R. Vargas-Yañez, G. Rodríguez-Arellanes, G.R Peña-Sandoval, C Toriello, A. Perez and M. R. Reyez-Montes. 1999. Environmental conditions Favouring Bat infection with histoplasma capsulatum in Mexican shelters. Am J. Trop. Med. Hyg. 61(6):914-919. • Taylos M.L, Reyes-Montes M. Chavez-Tapia C. B. Curiel-Quesada E. Duarte-Escalante E. Rodríguez-Arellanes G. Peña-Sandoval G. R., and Valenzuela-Tovar F. 2000. Ecology and molecular epidemiology findings of Histoplasma capsulatum, in Mexico. Res. Adv. In Microbiology. 1:29-35.