Published Date: 1997-12-24 23:50:00
Subject: PRO/AH> Scabies, chimpanzees - Tanzania (Gombe Nat. Park) (02)
Archive Number: 19971224.2542
SCABIES, CHIMPANZEES - TANZANIA (GOMBE NATIONAL PARK) (02)
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Scabies, chimpanzees - Tanzania (Gombe National Park) 971219004021Date: Wed, 24 Dec 1997 01:45:14 +1000 (EST)
From: Richard Speare <Richard.Speare@jcu.edu.au>
I have not worked with scabies in chimps, but I have dealt with scabies in
other primate species (humans) and in other animal species. The following
may be of some interest.
>We seek advice about further treatment, especially should we make an effort
>to treat all chimps?
Your descriptions of the clinical signs of the disease, epidemiology, and
response to treatment are typical of scabies in intimate groups of many
animal species, including humans. Ivermectin can be used to eradicate
scabies from closed groups. Since infection with scabies can be
asymptomatic, treatment of all members of the group at the same time is the
best strategy. Treatment of symptomatic animals only will be unlikely to
eradicate the scabies mite, and scabies will be likely to remain an ongoing
problem in the group. I would recommend treatment of all members with 0.2
mg/kg of ivermectin orally given on the same day or as close together as
possible. Re treatment in 10 days should ensure an excellent response, and
could eradicate the mite from the group.
The scabies mite has little tolerance for the external environment and is
unable to survive for greater than a day or so off the host even in ideal
conditions. I am not aware of any studies that have examined the survival
of _Sarcoptes_ in the wild. I would imagine this environment would be
more hostile than the floors and beds of human habitations. Hence in theory
eradication is achievable by multiple treatments with ivermectin.
>What are the consequences of widespread use of Ivermectin?
Widespread use of ivermectin at the dose given (0.2 mg/kg) should have no
ill effects on the chimps. Primates appear able to tolerate doses of 0.8
mg/kg without ill effects. Additionally, ivermectin will kill lice and some
gastrointestinal nematode parasites, particularly oxyurids, ascarids,
_Strongyloides_, and may have some impact on other nematodes. This should
improve the health of the chimps.
>We would also appreciate ideas about possible origin of the >disease and
information about similar outbreaks in other places.
The number of species of _Sarcoptes_ has yet to be clarified. Morphological
differences are not obvious, and current ideas are that the taxon is a
single species, _Sarcoptes scabiei_, with different strains, some showing
better adaption to particular host species than others. DNA work is in its
infancy, but several groups are working on it, but none in Africa as far as
I am aware.
_Sarcoptes scabiei_ has been found in other African mammals. In South
Africa _Sarcoptes_ has been found in leopards, lions, impala, giraffe,
wildebeste. Nothing is known of the epidemiology including predator-prey
transmission.
As to source in the chimps? The general lessons from scabies epidemiology
is that the most important source is the same host species. Sustainable
epidemics occur in these cases. Strains from other more distantly related
hosts rarely result in epidemics. Perhaps with the chimps, human to chimp
transmission or predator-prey interactions (via other primates or gazelles)
may have allowed the mite to enter the chimp population. Of these two
possibilities I would predict that a strain from a primate source would have
the better chance of entering the chimp population and establishing an
ongoing epidemic.
>It has been suggested to us that the chimps may have been immunosuppressed
>by another agent that then rendered them susceptible to the skin disease.
>How can we investigate this possibility in a non-invasive manner?
Scabies mites do not need an immunosuppressed host to cause serious disease.
The epidemic could be explained totally by a well-adapted strain of
_Sarcoptes scabiei_ entering a population of chimps not previously exposed
to it. Epidemics of this nature have been well documented in populations of
other wild animals.
--
Rick Speare
Department of Public Health and Tropical Medicine
James Cook University
Townsville
AUSTRALIA
Phone: -61-(0)77-225700
Fax: -61-(0)77-225788
email: Richard.Speare@jcu.edu.au
[It is good to hear that infection with _Sarcoptes scabiei_ does not
necessarily imply the chimp population has a significant proportion of
immunosuppressed animals. I hope it is possible to treat all these chimps
simultaneously or nearly so. If that task can be accomplish, ProMED-mail
would like to occasionally provide updates on the condition of chimps.
Thanks, Rick for a very comprehensive answer. This is the way ProMED-mail
should work. Thanks also to those who wrote in concerning treatments. I am
collecting them for another posting. - Mod.PC
..................................pc/es
--
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