Disseminated toxoplasmosis in a captive slender tailed meerkat

Heindrich Snyman, Sherry Davidson, Ron Mergl

Animal Health Laboratory, University of Guelph, Guelph, ON (Snyman); Niagara Falls Animal Medical Centre, Niagara Falls, ON (Davidson, Mergl). 

AHL Newsletter 2020;24(3):15.

A ~ 2 year old, intact male, slender-tailed meerkat (Suricata suricatta) from a captive zoo colony presented with sudden acute bilateral hind limb ataxia.  The hind limbs did not reveal any observable pain response and no obvious central proprioceptive deficits were apparent although a full detailed neurological examination was difficult in this animal.  Immediate differentials included trauma (spinal fracture/luxation) with spinal cord compression or some other cause of central nervous system inflammation.  The ataxia progressively worsened to paralysis and due to a lack of clinical response and a poor prognosis, the animal was euthanized.

An in-clinic necropsy was performed, revealing a regional area of sublumbar intramuscular hemorrhage at the level of L4 that was consistent with localized trauma.  Other findings included mottled congestion of the ventral apical surfaces of the heart, bilateral pallor of the kidneys, and pale mottling of the splenic parenchyma.  A broad array of representative tissues were collected in formalin and submitted to the Animal Health Laboratory for histopathology.

Histological sections of the brain and spinal cord contained multiple randomly scattered ~ 50 to 200 µm foci of malacia and gliosis (Fig. 1) with associated lymphoplasmacytic perivascular cuffing and few similar loose meningeal infiltrates of lymphocytes, plasma cells and macrophages.  The heart contained multiple dense ~ 50 to 350 µm diameter coalescing interstitial aggregates of macrophages, lymphocytes, plasma cells, and rare scattered neutrophils with regional associated myofiber degeneration and necrosis (Fig. 2).  Similar inflammatory aggregates were also scattered throughout the liver with accompanying acute hepatocellular necrosis, as well as the kidneys.  Visceral lymph nodes contained small numbers of draining neutrophils and macrophages.  The spleen appeared unremarkable and splenic mottling was attributed to red pulp congestion and barbiturate euthanasia.

The progressive neurological decompensation in this meerkat was attributed to this pleocellular and necro-inflammatory disease that was highly suggestive of infection with Toxoplasma gondii. Disseminated toxoplasmosis was confirmed by IHC staining with localization of T. gondii antigens to inflammatory foci within the brain (Fig. 3). 

Meerkats are members of the mongoose family and are considered highly susceptible to infection with T. gondii.  A number of high mortality outbreaks in captive zoo settings have been described.  Similar to other domestic animal species, transmission is through the fecal-oral route via ingestion of contaminated feed.  This occurs commonly in captive settings where feral cats can be attracted to feed in enclosures, which allows for the subsequent shedding of infectious oocysts into the environment.

Although the clinical presentation did not reveal any central nervous system deficits in this case and a traumatic incident was initially suspected, the multifocal nature of this disease often results in widely varied clinical presentations which can complicate antemortem diagnosis.  Therefore, given the species predilection, toxoplasmosis should always be considered in any cases of central or peripheral neurological disease or acute unexplainable death in meerkats.   AHL 

Figure 1. Focus of malacia and gliosis in the brain (arrow) (H&E).

Figure 2. Interstitial myocarditis comprised of aggregates of macrophages, lymphocytes and plasma cells. (H&E)

Figure 3. Positive IHC staining for Toxoplasma gondii antigen in a malacic and gliotic focus in the brain (arrows)

References

1. Molly E, et al. Chapter 14 - Procyonidae, Vivverridae, Hyenidae, Herpestidae, Eupleridae, and Prionodontidae.  In: Pathology of Wildlife and Zoo Animals, 1st ed. Terio K, McAloose D and St. Leger, J, eds. Elsevier, 2018: 315.

2. Juan-Sallés C, et al. Epizootic disseminated toxoplasmosis in captive slender-tailed meerkats (Suricata suricatta). Vet Pathol 1997;34(1):1-7.

3. Basso W, et al. Isolation and molecular characterization of Toxoplasma gondii from captive slender-tailed meerkats (Suricata suricatta) with fatal toxoplasmosis in Argentina. Vet Parasitol 2009;161(3-4):201-6. 

4. Burger M, et al. Fatal disseminated toxoplasmosis in a zoological collection of meerkats (Suricata suricatta). J S Afr Vet Assoc 2017; Mar 31;88(0):e1-e5.

We wish to express our sincere condolences to the Niagara Falls Animal Medical Centre on the passing of our colleague and friend, Dr. Ron Mergl.   AHL