Biology Reference
In-Depth Information
Protobothrops elegans
,
P. mucrosquamatus
) have successfully established alien
populations on Okinawa raises a potentially more serious health issue than is presented
by
B. irregularis
in Guam. The two alien vipers of the genus
Protobothrops
are more
aggressive than the native
P. flavoviridis
, and
P. elegans
has already been calculated to
have a nine-fold greater rate of human envenomations than the native species
(Nishimura, 2005). It has been estimated that once the related
P. mucrosquamatus
expands over much of Okinawa in the next century it will cause between 112-258 bite
cases annually, much higher than the approximately 60 annual cases caused by its native
congener (Nishimura, 2005). Variance in these estimates depends on how far and how
fast the alien viper spreads as well as how aggressive it truly proves to be as human-
contact frequency increases. Other dangerously venomous snakes have been introduced
intentionally or accidentally through the pet trade to numerous other jurisdictions
(Appendix A), and their potential to create grave health risks should be obvious.
A similar threat is posed, but not yet realized, by alien populations of large con-
stricting snakes. Pythons (
Python molurus
) are now established in southernmost
Florida, and population densities are high and increasing. This species attains a length
of at least 7 m, is known to eat leopards in its native range (C.H. Pope, 1935), and can
be exceedingly cryptic. Several instances of pythons killing and eating alligators
(
Alligator mississippiensis
) in the Everglades are already documented. Although it is
unlikely to be a frequent occurrence, it seems fairly likely that a visitor to Everglades
National Park or surrounding area will eventually be killed by one. Similar concerns
would pertain to other massive snakes (
Python reticulatus
,
P. sebae
,
Eunectes
spe-
cies) should they become established in Florida or other localities.
Flinders Island spotted fever is a recently recognized human rickettsiosis (R.S.
Stewart, 1991). Endemic reptile ticks (
Aponomma hydrosauri
) have been identified
as a reservoir, and possibly a vector, of the disease (Stenos et al., 2003; Whitworth
et al., 2003). Although the rickettsia, ticks, and reptile hosts are all native to the
system studied, the potential for a reptile-borne tick to vector a human disease is
newly recognized and raises the possibility that other, currently unrecognized,
human diseases may accompany the widespread dispersal of reptile ticks via the pet
trade. This may be particularly obvious in the case of the African tick
Amblyomma
variegatum
, sometimes vectored by
Varanus
lizards, and known to carry the human
disease agent
Rickettsia africae
(Burridge, 2001). An outbreak of human Q fever
was associated with the handling and removal of alien ticks from imported reptiles
and is suggestive of a possible connection between the two, but direct evidence for
a causal relationship remains lacking (Burridge et al., 2000a; Burridge, 2001).
Alien frogs (
Eleutherodactylus johnstonei
) and toads (
Bufo marinus
) in
Barbados have been reported to host serovars of
Leptospira interrogans
that are
pathogenic in humans, livestock, and domestic dogs (Everard et al., 1988, 1990).
Everard et al. (1990) argued that amphibians may be more involved in human
leptospirosis epidemiology than currently appreciated, but this supposition remains
uninvestigated. Similarly, it has been noted that cane toads can carry extremely high
levels of pathogenic
Salmonella
and related bacteria (O'Shea et al., 1990; Thomas
et al., 2001), as well as pathogenic
Leptospirosis
(Babudieri et al., 1973; Everard et al.,
1980, 1983, 1988), but it is unknown whether wild populations of this species have
