A zoonosis is any infectious or parasitic disease of animals that can be transmitted to humans or from human to animals (reverse zoonosis). Many disease organisms can infect only humans or particular animals, but zoonotic organisms are more flexible and can adapt themselves to many different species.
Bats are natural carriers or vectors of several zoonotic pathogens including rabies, severe acute respiratory syndrome (SARS), Henipavirus and possibly even ebola virus. Rabies is mostly transmitted through direct physical contact with its victim, but it is also possible for the bat rabies virus to infect humans through airborne transmission. According to the World Health Organization (WHO) bat rabies has emerged as a public health problem in the Americas and Europe in the past few years. For the first time in 2003, more people in South America died from rabies caused by wildlife, particularly bats, than from dogs. Rabies is a viral neuroinvasive disease that causes inflammation in the brain; deadly if left untreated.
Birds can be carriers of diseases such as psittacosis, salmonellosis, campylobacteriosis, the avian tuberculosis, bird flu, giardiasis and cryptosporidiosis. Some of these can be transmitted to humans, the avian influenza or bird flu posing the most serious health threat. Just like “swine flu, “dog flu and human flu,” bird flu refers to an illness caused by any of the various strains of influenza viruses. Health experts are concerned that co-existence of flu viruses of birds and humans will create a new virulent influenza strain that can be easily transmissible and deadly to humans. When an outbreak started in 2003, at least 200 people had died in Indonesia, Vietnam, Laos, Romania, China, Turkey and Russia due to the highly pathogenic Influenza A virus subtype H5N1.
Dogs may be man’s best friend but in many parts of the world rabies from dog bites poses a serious threat to human lives especially children. According to the WHO, an estimated 31,000 people die from dog rabies in Asia annually; in Africa, the yearly death toll is 24,000. Rabies caused by dog bites is responsible for more than 14 million course of post-exposure treatment worldwide to prevent the onset of disease. Up to 60% of dog bite victims are children below 5 years old. Rabies can also be caught by eating rabid dog meats. Once the symptoms of the disease develop, rabies can be deadly. Dogs can also transmit toxocariasis in humans, which can cause blindness and human hookworm.