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Monday, December 4, 2017

Reverse zoonosis. How human pathogens affect animals.

Reverse zoonosis. The fact that diseases can pass from humans to animals is, perhaps, not such a surprise. An estimated 61.6 percent of human pathogens are regarded as multiple species pathogens and are able to infect a range of animals. Also, over 77 percent of pathogens that infect livestock are multiple species pathogens. One of the earliest studies demonstrating reverse zoonosis was conducted in 1988 and looked at dermatophytes - fungi that cause superficial infections of the skin, nails, and hair - including Microsporum and Trichophyton. The authors found that these fungi could be transmitted from animal to animal, human to human, animal to human, and human to animal. From 2000, studies began to emerge investigating the ability of certain parasites to pass from human to animal, including Giardia duodenalis (the parasite responsible of giardiasis), and Cryptosporidium parvum (a microscopic parasite that causes the diarrheal disease cryptosporidiosis).Reverse zoonosis. A study, published in the journal Veterinary Microbiology in 2006, looked at methicillin-resistant Staphylococcus aureus (MRSA) in pets and its transmission between humans and animals.The paper mentions a specific case in which a couple was repeatedly infected with MRSA. The re-infections only stopped once their dog was identified as the source and treated. It is presumed that the dog was initially infected by the couple and then passed the infection back to them each time they had been successfully treated. The emergence of MRSA in household pets is of concern in terms of animal health and the potential for animals to act as sources of infection or colonization of human contacts.Reverse zoonosis. A paper, published in 2004, describes the case of a 3-year-old Yorkshire terrier who arrived at the University of Tennessee College of Veterinary Medicine with anorexia, vomiting, and a persistent cough. After running a barrage of tests - including, sadly, an eventual postmortem - the authors concluded that it had contracted tuberculosis (TB) (Mycobacterium tuberculosis). The dog's owner had been receiving treatment for TB for 6 months. This was the first documented transmission of TB from human to canine. In 2009, the first recorded case of fatal human-to-cat transmission of the H1N1 flu virus occurred in Oregon. The owner of the cat had a severe case of influenza and had to be taken to the hospital. Her cat - an indoor cat with no exposure to other people or animals - later died of pneumonia caused by an H1N1 infection. Details of the case were published in the journal Veterinary Pathology. In 2011 and 2012, researchers identified more than 13 cats and one dog with pandemic H1N1 infection that appeared to have come from human contact. Interestingly, the animals' symptoms were similar to those experienced by human carriers - rapidly developing respiratory disease, a lack of appetite and, in some cases, death.