Cryptococcosis: An Enigmatic Mycosis of Humans and Animals

Abstract

Zoonoses with multiple etiologies affecting immunocompromised hosts have become a matter of concern presently, among the physicians and veterinarians. Among the zoonoses, cryptococcosis is considered a common and important mycozoonosis of global significance mainly affecting HIV/ AIDS patients. Cryptococcosis is primarily caused by Cryptococcus neoformans and Cryptococcus gattii, which are found in the soil contaminated with avian droppings or eucalyptus trees and decaying woods. Cryptococcus neoformans can survive in the saprobic environment for about 20 years. The respiratory tract is recognized as the principal mode of entry of the pathogen, and the source of infection is exogenous. It is believed that humans and animals acquire cryptococcal infection from saprobic reservoirs. Cryptococcosis occurs in sporadic and epidemic form resulting in high morbidity and mortality in the susceptible hosts. The disease is most often found in cats but has also been reported in cattle, dogs, horses, sheep, goat and other animals. Cryptococcosis is the first manifestation of HIV infection in 26 to 45% of patients, and recent data indicate that C. neoformans appears to potentiate HIV infection. Cryptococcal meningitis alone kills approximately 624,000 people in the world annually. The direct demonstration of the pathogen in the clinical specimens and its isolation in pure and luxuriant form remains the “gold standard” to the diagnosis of cryptococcosis. The routine application of Pal’s sunflower seed medium and Narayan stain in public health and microbiology laboratories will certainly help in the study of this enigmatic mycosis in humans as well as in animals.