Fatal disseminated toxoplasmosis in an immunocompetent cat

Susanna S Nagel,Johannes P Schoeman,June H Williams

doi:10.4102/jsava.v84i1.299

Abstract

A 10-year-old domestic short hair cat was referred for investigation of anorexia and polydipsia of 3 days' duration. Clinically the cat was obese, pyrexic (39.8 °C), had acute abdominal pain and severe bilirubinuria. Haematology and serum biochemistry revealed severe panleukopenia, thrombocytopenia, markedly elevated alanine aminotransferase (ALT) and five-fold increased pre-prandial bile acids. Ultrasonographic evaluation of the abdomen did not identify any abnormalities. Serum tests for feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) were negative. Broad-spectrum antibiotic treatment for infectious hepatitis was to no avail; the cat deteriorated and died 72 h after admission. Necropsy revealed mild icterus and anaemia, severe multifocal hepatic necrosis, serofibrinous hydrothorax, pulmonary oedema and interstitial pneumonia. Histopathology confirmed the macroscopic findings and revealed multifocal microgranulomata in the brain and myocardium, as well as areas of necrosis in lymph nodes and multifocally in splenic red pulp. Long bone shaft marrow was hyperplastic with a predominance of leukocyte precursors and megakaryocytes and splenic red pulp showed mild extramedullary haemopoiesis. Immunohistochemical staining for Toxoplasma gondii was strongly positive, with scattered cysts and tachyzoites in the liver, lymph nodes, spleen, lungs, brain, salivary glands and intracellularly in round cells in occasional blood vessels. Immunohistochemical staining for corona virus on the same tissues was negative, ruling out feline infectious peritonitis (FIP). Polymerase chain reaction (PCR) on formalin-fixed paraffin-wax embedded tissues was positive for Toxoplasma sp., but attempts at sequencing were unsuccessful. This was the first case report of fulminant disseminated toxoplasmosis in South Africa, in which detailed histopathology in an apparently immunocompetent cat was described.

Highlights

Toxoplasma gondii is a zoonotic obligate intracellular coccidian protozoon known to cause occasional clinical illness in cats and dogs
Adult humans who are not immunocompromised rarely show clinical signs of toxoplasmosis; cases of pneumonia in immunocompetent individuals have been reported in French Guiana and were attributed to genetically atypical highly virulent strains (Carme et al 2002)
Haematology revealed severe leukopenia (2.94 × 109/L, reference range 7.0–20.5), with degenerative left shift, severe mature neutropenia, moderate lymphopenia, moderate monocytopenia and severe thrombocytopenia (69.00 × 109/L, reference range 300–600). These results suggested a http://www.jsava.co.za suppressed immune state, possibly caused by overwhelming infection

Summary

Introduction

Toxoplasma gondii is a zoonotic obligate intracellular coccidian protozoon known to cause occasional clinical illness in cats and dogs. In the asexual stage (sporozoites, tachyzoites and bradyzoites), T. gondii has little intermediate host specificity, being able to parasitise homeotherms including some birds and all mammals (Cenci-Goga et al 2011), but usually only develop disease if in an immunocompromised state, as is the case in cats (Davidson et al 1993; Foster et al 1998; O’Neil et al 1991; Sato, Yoshiki & Iwamoto 1994). IMH staining was found to be strongly positive on small pieces of most tissues, with bradyzoites-containing cysts and free tachyzoites visualised in liver, pancreatic lymph node (Figure 8), spleen, brain, heart, lungs, and intracellularly in some mononuclear inflammatory cells in occasional blood vessels. Wax-embedded formalin-fixed tissues, including pancreas, pancreatic and mesenteric lymph nodes, liver and lung were sent to the laboratory of Dr J.P. Dubey for PCR testing and possible sequencing for typical or atypical strains. DNA was successfully extracted using the method of Weiss et al (2011), but further sequencing for an atypical strain was unsuccessful

Discussion

Findings

Conclusion