Infections that are secondarily transmitted from animals to humans are referred to as zoonoses and can seriously affect personnel and their research. 

While most infectious agents show a considerable degree of species specificity, they also may, from time to time, vary widely in virulence and in their capacity to break through species barriers. Thus, infections that have not commonly been considered to be zoonotic hazards may sporadically affect susceptible persons or animals. Persons potentially at higher risk are those who suffer from defective immune systems and those who are under severe stress or who have non-overt clinical disease. Numerous pathogenic microorganisms, such as those responsible for tuberculosis, brucellosis, rabies, etc., which are normally perpetuated by direct transmission from one or more species of vertebrate animals, are also readily transmissible to humans. 

Transmission of infections from animals to humans can generally be avoided through proper veterinary care and adherence to SOPs for control of transmission. However, when animals are obtained from areas in which zoonotic diseases are known to exist, e.g., in NHP (Non-Human Primate) acquired from the wild, special attention is required.  Work involving exposure to hazardous microorganisms might require prior immunization of the staff, if a vaccine is available. 

Caution should be exercised in assigning women of childbearing status to animal care duties that might expose them to potential or known teratogens. For example Toxoplasma gondii, a protozoan that infects most species of warm-blooded animals, including humans, is spread primarily by oocysts shed in cat feces. These oocysts sporulate in two to four days and may survive for more than a year. Human toxoplasmosis can result in spontaneous abortion, prematurity, stillbirth or congenital defects. 

The life cycle of the causative organisms implicated in a number of indirect zoonoses may involve transmission through one or more other vertebrate and/or invertebrate intermediate hosts before affecting humans (for example, in taeniasis, tularemia, and vesicular stomatitis). Amongst invertebrate vectors of zoonotic disease, the biting insects are the main offenders. A list of some of the diseases transmitted to humans from animals can be found in Appendix VII of the CCAC guide ( http://www.ccac.ca/en/CCAC_Programs/Guidelines_Policies/GUIDES/ENGLISH/V1_93/CHAP/CHVIII.HTM#8C ). 

The role of cold-blooded vertebrates in the epidemiology of zoonoses should not be overlooked. In particular, turtles infected with salmonella may constitute a human health hazard in the student laboratory as well as in the animal facility.