No: 09 September 2007

ZOONOSES
DESCRIPTION
The World Health Organization defines Zoonoses (Zoonosis, sing.) as "Those diseases and infections which are naturally transmitted between vertebrate animals and man".

CLASSIFICATION
Zoonoses can be classified in many ways:

  • According to the mechanism of transmission
    1. Anthropozoonoses: Infections transmitted to man from lower vertebrates (ex: rabies, toxoplasmosis)
    2. Zooanthropozoonoses: Infections transmitted from man to animals (ex: diphteria, amebiosis)
    3. Amphixenoses: Infections maintained in both man and lower vertebrates, and may be naturally transmitted in either direction (ex: Staphilococcus, mycobacteria)
  • According to the life cycle
    1. Direct Zoonoses: Transmitted from infected vertebrate host to a susceptible vertebrate host by direct contact or by a mechanical vector. No developmental change or propagation of the organism occurs during the transmission (ex: Rabies, trichinosis, and brucellosis)
    2. Cyclozoonoses: Requires more than one vertebrate host, but no invertebrate host.  (ex: Echinococcosis, human taeniasis and Pentastoma infections)
    3. Metazoonoses: Agent multiplies, develops, or both in an invertebrate host before transmission to a vertebrate host is possible. (This means that a definite prepatent or incubation period must be completed before transmission.) (ex: Arboviruses, plague, and schistosomiasis)
    4. Saprozoonoses: To transmit these infections a non-animal development site or reservoir is required, such as food plants, soil, or other organic material. (ex: larva migrans and some of the mycotic diseases)
  • According to the etiology (mostly used)
    1. Bacterial zoonoses: Botulism, tuberculosis
    2. Viral zoonoses: Rabies, Hepatit A virus
    3. Fungal zoonoses: Aspergillosis, actinomycosis
    4. Protosoal zoonoses: Anaplasmosis, babesiosis, malaira
    5. Helmintic zoonoses: Trichinosis, echinococosis, taeniasis

ZOONOSES AND THE EUROPEAN PARLIAMENT AND COUNCIL
In November 2003, the European Parliament and Council defined Lists A and B of the Directive 2003/99/EC which specifies those zoonotic agents and diseases considered relevant to the EC. List A, are those zoonoses which must be included in monitoring, and List B defines viral, bacterial and parasitic zoonoses and zoonotic agents that are to be monitored according to the epidemiological situation.

List A- Zoonoses and zoonotic agents to be included in monitoring
  • Brucellosis and agents thereof
  • Campylobacteriosis and agents thereof
  • Echinococcosis and agents thereof
  • Listeriosis and agents thereof
  • Salmonellosis and agents thereof
  • Trichinellosis and agents thereof
  • Tuberculosis due to Mycobacterium bovis
  • Verotoxigenic Escherichia coli
List B- List of zoonoses and zoonotic agents to monitored according to the epidemiological situation
  • Viral Zoonoses
    • Calicivirus
    • Hepatitis A virus
    • Influenza virus
    • Rabies
    • Viruses transmitted by arthropod
  • Bacterial zoonoses
    • Borreliosis and agents thereof
    • Botulism and agents thereof
    • Leptospirosis and agents thereof
    • Psittacosis and agents thereof
    • Tuberculosis other than in list A
    • Vibriosis and agents thereof
    • Yersiniosis and agents thereof
  • Parasitic zoonoses
    • Anisakiasis and agents thereof
    • Cryptosporidiosis and agents thereof
    • Cysticercosis and agents thereof
    • Toxoplasmosis and agents thereof
    • Other zoonoses and zoonotic agents
  • ther zoonoses and zoonotic agents

TRANSFER WAYS OF ANIMAL DISEASES TO HUMAN

  • Human Consumption of Raw or Undercooked Meat, Poultry, or Seafood

For example, if meat contains harmful bacteria, and it is not thoroughly cooked to kill the bacteria, foodborne illness/disease may result once the food is eaten.

  • Human Being Bitten or Stung by an Insect or Animal

For example, dog bites may seriously injure tissues and can also transmit bacterial infections and rabies, a disease of viral origin. The bite of a diseased rat may transmit any of several diseases to man, including plague, salmonellosis, leptospirosis, and rat-bite fevers; the bites of venomous snakes and fish can lead to human discomfort and death.

  • Human Contact with the Flesh of an Animal

The flesh of various types of fish is toxic to man. For example, Japanese puffers contain the poisonous chemical compound tetrodotoxin; scombroid fish harbor Proteus morganii, which causes gastrointestinal diseases; and mullet and surmullet can cause nervous disturbances.

EMERGING ZOONOSES
Contrary to "lingering" zoonoses, public awareness of "emerging" zoonoses is very high. The WHO/FAO/OIE joint consultation on emerging zoonotic diseases held in Geneva, 3-5 May 2004, defined an emerging zoonosis as "a zoonosis that is newly recognized or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range". Emerging zoonotic diseases have potentially serious human health and economic impacts and their current upwards trends are likely to continue.
Examples are avian influenza, Bovine Spongiform Encephalitis (BSE) and the Nipah virus. Some of the "lingering" zoonoses are re-emerging in some regions, although they seem to attract less public awareness. Brucellosis, dog rabies and parasitic diseases such as cysticercosis/taeniasis and echinococcosis/hydatidosis for example.
Many factors lead to the emergence of zoonotic diseases. Environmental changes, human and animal demography, pathogen changes and changes in farming practice are a few of them. Social and cultural factors such as food habits and religious beliefs play a role too.

References
http://www.middlebury.edu/administration/stss/animal_facility/veterinary/zoonosis.htm
http://homepage.uludag.edu.tr/~mtayar/bakteriyel.htm
http://www.medvetnet.org/cms/templates/doc.php?id=28

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