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Last
updated on September 12, 2010
Disease
Surveillance, Transmission, Latency, Persistence, Incubation
Diseases that are "notifiable" to CDC List of Notifiable DiseasesThe list of nationally notifiable diseases is revised periodically. For example, a disease might be added to the list as a new pathogen emerges, or a disease might be deleted as its incidence declines. Public health officials at state health departments and CDC continue to collaborate in determining which diseases should be nationally notifiable. The Council of State and Territorial Epidemiologists (CSTE), with input from CDC, makes recommendations annually for additions and deletions. Although disease reporting is mandated (i.e., by legislation or regulation) at the state and local levels, state reporting to CDC is voluntary. Thus, the list of diseases considered notifiable varies slightly by state. All states generally report the internationally quarantinable diseases (i.e., cholera, plague, and yellow fever) in compliance with the World Health Organization's International Health Regulations.Infectious Diseases Designated as Notifiable at the National Level During 2008(from the CDC web site http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5754a1.htm)
Note: some diseases that veterinarians know are "reportable" are
not included on this list, i.e. monkeypox. This is covered in the import
regulations for NHPs.
Surveillance Techniques
There is disagreement
over how quarantined animals should be housed. A Special Topic Review by Rehg
and Toth {3965} summarized their institution’s quarantine procedures for rodents,
particularly mice. Quarantined rodents should be kept in a separate physical
facility from the resident animals, ideally. If this is not possible they
should be kept in an area under negative pressure, or in flexible film
isolators. Durfee et al claimed that animals from approved vendors could be
accepted directly into the resident colony as long as periodic monitoring is
done to pick up any unsuspected organisms.{3700} On the other hand, Hessler et
al believe that rodent quarantine should be conducted under BSL-3-like
conditions, including separate ventilation system, double doors, and
autoclaving materials into and out of the facility. Alternatively, Hessler
suggests that separate rooms with ventilated caging and microisolators can be
used.{3741} Small agreed that animals from reputable vendors could be placed
directly into the room in which the experiment is to take place, claiming that
a passive quarantine of 4-6 weeks allows non-persistent murine viruses such as
RCV/SDAV and Sendai virus to run their course. In an active quarantine in which
animals are presumed to be contaminated (i.e. if the vendor is suspect or the
animals come from non-traditional sources), they should be housed in plastic
Trexler isolators, Illinois cubicles, or Horsfall-Bauer units and tested
serologically.{3956} If the experimental rodents cannot
be used for testing (because they are fragile, immunocompromised or institutional
policy prohibits it), sentinel animals must be substituted. These may be of the
same source population as the experimental animals, or they may be of a
different strain and coat color to distinguish them from the experimental
animals. There is general agreement that mice of susceptible strains and
varying ages should be used in quarantine programs. Females are most often used
because they fight less and will not cause pregnancy if cohabited with other
animals, but sex predilection should be kept in mind.{3956}{3965} Sentinels can
be exposed purposely to the other animals by cohabitation, or by purposely
contaminating their bedding with that of other animals. For bedding
contamination to work, the organism of interest must be shed in the feces, be
stable in feces, and be of sufficient numbers to infect the sentinels.{3965}
Well-kept records are essential to
any QA program. A pattern may be seen to emerge when deaths occur that are not associated
with experimentation. Clinical records should be maintained for rodent rooms in
the same way that individual records are kept for some larger species. Charts
depicting the arrangement of animal room racks may help in tracking the
infected animal’s proximity to others in the room. In addition, floor plans may
be used to indicate the flow of supplies, people, water and air to help
pinpoint management problems.{3956} A different method of finding
infectious organisms in animal rooms is to use PCR on environmental surfaces.
Room air filters, for example, may be a good source of parvoviruses, which remain
in the environment for at least 6 months.{4026} Sample size
The question of the
right number of animals to sample is challenging because it is always too high
to be deemed affordable. The correct prevalence of the disease of interest is
also problematic, because the goal is zero and most vendors (and possibly
institutions) claim that that is the correct prevalence in their colonies. This table may be used to help
determine the number of animals to be sampled. It predicts the number of animals
required to detect a single case of disease in a population of ³
100 animals. The acceptable confidence limits and the assumed percentage of
infected animals present must both be known.{3956} If, for example, the assumed
prevalence of the disease in the population is only 1%, testing 200 animals
will only yield an 87% confidence of picking up the disease. Most authors seem
to accept that testing 5-10 animals in the population will detect a disease if
the prevalence is as high as 30%. The table and the formula were first
published in 1976{3966} and were based on personal communication. Probability
of Detecting Infection in a Sample of Animals
Confidence limits are tabulated for assumed
infection rate in top row
log (1-assumed % infection rate) |
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©1999, Janet Becker Rodgers, DVM, MS, DipACLAM, MRCVS All rights reserved. Comments? Send an email to janet.rodgers@vet.ox.ac.uk |