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Investigation of Chronic Disease in a Captive Mara Colony. Mexico. Index Case. July 21, 2001 2 year old captive born male mara ( Dolichotis patagonum ) died shortly after presenting with weakness and anorexia. Index Case-con’t.

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index case
Index Case
  • July 21, 2001
    • 2 year old captive born male mara (Dolichotispatagonum) died shortly after presenting with weakness and anorexia
index case con t
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
case confirmation
Case Confirmation
  • Gross necropsy findings
  • Histological findings
  • Other testing
    • Special stains
    • Transmission electron microscopy
    • Organism isolation
    • Exoantigen test
    • Immunohistochemistry
establishing endemic levels
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
is there an outbreak
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.
descriptive epidemiology
Descriptive Epidemiology
  • Herd history
  • Environmental factors
herd history
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
environmental factors
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)
subsequent cases
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
case 2
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.
is this an outbreak
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
immune status and environment
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
  • Unusual susceptibility of this species to the disease
  • Low immunological status of the group
    • Predisposing them to disease
  • High environmental contamination
investigate hypothesis
Investigate Hypothesis
  • Review literature for similar cases
  • Environmental Investigation
literature review
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
environmental investigation
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
environmental investigation1
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
treatment and intervention
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
long term
Long Term
  • Control of immune status of the colony
    • Review sex ratio and demographics
    • Review genetics
  • Monitor wild bat colonies within the park
  • 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.