Zoonoses: Infectious Diseases Transmissible From Animals and Humans, Fourth Edition

Dermatophytoses are chronic fungal infections caused by dermatophytes, that is, keratinophilic fungi that are able to utilize keratin-containing structures (hair, nails, scales, etc.) from humans and animals. They belong to the genera Epidermophyton, Microsporum, and Trichophyton of the family Arthrodermataceae. Individual species may be anthropophilic, zoophilic, or geophilic. Zoophilic species from warm-blooded animals with overt or latent infections may, if transmitted to humans, give rise to severe cases of dermatitis. Transmission from human to human is possible, although infectivity decreases with each passage and dies out after three to four passages. Anthropophilic dermatophytes, such as Trichophyton rubrum, T. tonsurans, and Epidermophyton floccosum, can also (although rarely) be transmitted from humans to animals, in whom they may cause skin diseases. In turn, these animals could be a source for human infections. The same chain may operate in primarily geophilic species, such as Microsporum racemosum and M. gypseum.

In the United States, approximately 4 to 5 million episodes of animal bites occur every year, resulting in approximately 300 000 visits to emergency departments, 10 000 hospitalizations, and 20 deaths, mostly among young children. In England and Wales, 200 000 people per year seek medical help in hospitals after dog bites; in France, the number is 500 000. In Germany, 35 000 people per year are bitten by dogs; 1 to 2% of them are treated in ambulatory care units.

Iatrogenic transmission of pathogens is generally possible for agents that circulate in the blood or infect tissues to be transplanted. Severe complications may arise, particularly if the agent is able to subsequently proliferate in the recipient. Apart from using contaminated tools, for instance, needles and syringes, iatrogenic transmission occurs mainly in the course of transfusion of blood or blood products and in organ transplantation. Major problems arise by the fact that usually relatively large amounts of agents are transmitted and the recipient is, in general, a sick person, impaired by an eventually reduced resistance or immunocompetence. Transmissions of the following zoonotic agents by transfusion of blood and blood products have been reported:

• Viruses: Colorado tick fever virus, dengue fever virus, West Nile fever virus, Ross River fever virus, herpes B virus, lymphocytic choriomeningitis virus, rabies virus, yellow fever 17D vaccine. HIVs originating from monkeys have been established as human infectious agents;
• Bacteria: Anaplasma phagocytophilum, Brucella spp. Campylobacter jejuni, Ehrlichia ewingii, Listeria monocytogenes, Rickettsia rickettsii, Salmonella, Yersinia enterocolitica;
• Parasites: Babesia spp., Leishmania spp., Plasmodium spp., Toxoplasma gondii, Trypanosoma cruzi, Trypanosoma gambiense, Trypanosoma rhodesiense.