As every year, during the last days, in Italy, several cases of bird flu in chickens were notified by Ministry of Health. Although it affects mainly poultry and other avian species, this disease is described as a zoonosis, in other words a disease that can be transmitted, occasionally and under specific conditions, from animals to humans.
The transmission of the disease can occur directly, via biological infected material of animal origin (skin, eggs, blood, mucus), or indirectly, through ingestion of contaminated food or transmission of the pathogen through a vector.
From this first description, it is evident that the risk is highest for people who work directly in contact with animals (veterinarians and farmers, for example). Even pets, and of course the wild animals, can be a source of infection for humans.
Zoonoses transmitted through the ingestion of contaminated food are also very common, such as the famous salmonellosis. Outbreaks of zoonotic diseases involving animals destined for human consumption also involve a relevant economic damage (as well as ethical, of course): during the outbreak of avian influenza in Italy in 2013 nearly 1.400.000 chickens were sacrificed.
Among the zoonoses transmitted by vectors, many diseases are particularly famous, such as malaria (transmitted by the mosquito) and the plague (transmitted by fleas). Usually this type of zoonoses are related to specific environmental and social situations, such as the presence of wetlands for malaria or a situation of social degradation for the plague.
Usually, humans are occasional hosts and their infection is not very useful for pathogens, because there is no trasmission of infection to other organisms (humans or animals). As example, rabies is transmitted from infected animals (dogs, cats, but also foxes and bats) to humans but it is uncommon human-to-human or human-to-animal infections. On the other hand, it is known that many diseases that today usually infect humans are caused by pathogens that have developed the ability to infect humans although before it had never occurred. One of the most reliable theories describe a similar origin for the HIV virus: this disease is well described in other animal species (such as FIV in cats) and it is believed that it may have been originally transmitted to humans by some African primates infected by a mutated virus.
I leave you with one final curiosity: not only animals can infect humans, but it can also be done in reverse: it is called reverse zoonosis or anthroponosis, such as tuberculosis that can be transmitted by humans to companion animals.
The transmission of the disease can occur directly, via biological infected material of animal origin (skin, eggs, blood, mucus), or indirectly, through ingestion of contaminated food or transmission of the pathogen through a vector.
From this first description, it is evident that the risk is highest for people who work directly in contact with animals (veterinarians and farmers, for example). Even pets, and of course the wild animals, can be a source of infection for humans.
Zoonoses transmitted through the ingestion of contaminated food are also very common, such as the famous salmonellosis. Outbreaks of zoonotic diseases involving animals destined for human consumption also involve a relevant economic damage (as well as ethical, of course): during the outbreak of avian influenza in Italy in 2013 nearly 1.400.000 chickens were sacrificed.
Among the zoonoses transmitted by vectors, many diseases are particularly famous, such as malaria (transmitted by the mosquito) and the plague (transmitted by fleas). Usually this type of zoonoses are related to specific environmental and social situations, such as the presence of wetlands for malaria or a situation of social degradation for the plague.
Usually, humans are occasional hosts and their infection is not very useful for pathogens, because there is no trasmission of infection to other organisms (humans or animals). As example, rabies is transmitted from infected animals (dogs, cats, but also foxes and bats) to humans but it is uncommon human-to-human or human-to-animal infections. On the other hand, it is known that many diseases that today usually infect humans are caused by pathogens that have developed the ability to infect humans although before it had never occurred. One of the most reliable theories describe a similar origin for the HIV virus: this disease is well described in other animal species (such as FIV in cats) and it is believed that it may have been originally transmitted to humans by some African primates infected by a mutated virus.
I leave you with one final curiosity: not only animals can infect humans, but it can also be done in reverse: it is called reverse zoonosis or anthroponosis, such as tuberculosis that can be transmitted by humans to companion animals.
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