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TICKS Dermacentor spp. -- Acarina, Ixodidae (Contacts) ----- CLICK on Photo to enlarge & search for Subject Matter with Ctrl/F. GO TO ALL: Bio-Control Cases
American Dog Tick.--The life cycle may be
completed in 1-3 years, and there seems to be little activity during winter
of in the hot summer. Adults are most
active in the spring and may live >2 years without food. This is the only stage known to infest
humans, dogs and domestic animals.
Small mammals, especially mice and rabbits, are considered to be the
principal hosts. Mating occurs on the
host. After engorging, they drop from
the host and the females deposit their eggs in protected places in masses of
4,000-6,500 eggs, after which they die. The eggs hatch into six-legged
larvae, which attach to a passing host.
After feeding for several days, they become engorged, drop tot he
ground, and molt to the nymphal stage.
When the nymph is ready to feed, it likewise seeks a host on which to
attach. When the nymph has become
engorged, it also drops to the ground where it molts to the adult stage. Both larvae and nymphs were observed to
live >one year in the absence of food (Smith et al. 1946). The encyrtid
parasitoid, Hunterellus hookeri Howard (= Ixodiphagus caucurtei du Buysson) was
introduced from France into the United States where it was propagated and
released on Naushon Island, Massachusetts, in an attempt to control the
American dog tick (Larrouse et al 1928).
Small numbers of nymphs of D.
variabilis parasitized by
the French strain of H. hookeri were released on Capers
Island, South Carolina in 1931 (Bishopp 1934). A larger effort was made on Martha's Vineyard Island, Mass.,
where ca. 90,000 females of H.
hookeri were released in two
locations on the island during 1937-39.
The strain of parasitoid used originated in Texas (Smith & Cole
1943). Larrouse et al.
(1928) reported that in the season following the releases of H. hookeri on Naushon Island immature parasitoids were found
in a single nymph of the dog tick and a single nymph of another tick
species. Subsequent surveys were
conducted in 1940 by Cobb (1942) and in 1941 by Smith & Cole (1943). In both cases a few parasitoids were
found, but none were recovered from the American dog tick. Both this species and Ixodes scapularis
Say were still observed in abundance; therefore, there was no evidence that
any success was achieved. Bishopp
(1934) reported recovery of the parasitoid from a single nymph of D. variabilis on Caper Island two years after release. In an assessment of results of release of
the parasitoid in Martha's Vineyard in 1937-39, Smith & Cole (1943)
recovered no parasitoids from ticks in the release areas and observed no
reduction in tick abundance that could be attributed to the parasitoid. A later report by Smith et al. (1946) also
indicates that the attempt was unsuccessful. The biology of H. hookeri was reported in Wood (1911) Cooley (1928, Cooley
& Kohls (1933) and Smith & Cole (1943), Cole (1965) and McMurtry
(1978). Rocky Mountain Wood Tick.--The Rocky Mountain wood tick is a vector of Rocky
Mountain spotted fever, a rickettsial pathogen caused disease that may be
fatal to humans, but is primarily harmful to wild animals. It can also carry tularemia, another
disease primarily of wild animals, but also infectious to humans. This tick is also responsible for tick
paralysis, which affects the motor nerves starting in the legs and gradually
spreading to the rest of the body.
This seems to result only if the tick feeds at the back of the neck or
the base of the skull, and removal of the tick usually results in
recovery. Dermacentor andersoni
occurs in the western United States, primarily in the Rocky Mountains and
also in Canada. Spotted fever occurs
in other areas, but its chief vector there is the American dog tick, D. variabilis (see McMurtry 1978). The eggs of D. andersoni are laid on the ground. They hatch in spring or early summer into
six-legged larvae and climb onto grass blades or other vegetation and attach
to passing animals, usually small rodents.
When fully fed in a few days, the larvae drop to the ground to molt to
the nymphal stage, which usually does not feed until the following spring,
when they attach to small animals, become engorged, and drop to the ground to
transform to the adult stage (McMurtry 1978). Though some adults may attach to hosts the same season, they
apparently pass the rest of the summer and winter in hiding and find a host
the following spring. Mating takes
place on the host, and when fully fed the female drops to the ground to
deposit her eggs. Only the adult
stage is known to attack humans and large animals (Cooley 1932). The encyrtid
parasitoid H. hookeri was brought to Montana
for colonization (Cooley 1928, Cooley & Kohls 1933). Over 4 million parasitoids were liberated
during 1927-32, mostly in Montana but also in Colorado, Oregon and
Idaho. Various methods were used,
including release of adult parasitoids, scattering parasitized nymphs in
grass and low vegetation, and liberating squirrels, which had been infested
with parasitized nymphs. The methods
for mass production are described by Morton (1928). Recovery of
parasitoids was made in only one instance in 1929, when a few which had
emerged from D. andersoni nymphs taken from
squirrels captured in the Bitter Root Valley of Montana (Cooley & Kohls
1933). Cole (1965) reported that no
reduction in the tick population was observed and no evidence has been
obtained that the parasitoids were established in nature. Other Ixodidae.--McMurtry
(1978) reported on other species of Ixodidae that were subjects of biological
control. Alfeev (1940) reported on an
experiment in which it was attempted to control Ixodes ricinus
(L.) and I. persulcatus Schulze in a 250-acre
pasture in the province of Leningrad, U.S.S.R. Hunterellus hookeri was obtained from
Montana in 1935 and propagated, and 2,600 adult parasitoids and 38,000
parasitized ticks were liberated. But
no recoveries were reported. REFERENCES: [Additional
references may be found at:
MELVYL Library ] Alfeev, N. I. 1940. The utilization of Hunterellus hookeri
How. for the control of the ticks Ixodes
ricinus L. and Ixodes persulcatus Sch. with reference to the peculiarities of
their metamorphosis under the conditions of the Province of Leningrad. In: Pavlovsky, 2nd Conf. Parasitol.
Problems, Nov. 1940. Akad. Nauk. S.S.S.R. Isv. 23-5. Bishopp, F. C. 1934. Records of hymenopterous parasites of
ticks in the United States. Wash.
Ent. Soc. Proc. 36: 87-8. Cobb, S. 1942. Tick parasites on Cape Cod. Science 95: 503. Cole, M. M. 1965. Biological control of ticks by the use of
hymenopterous parasites. A review. World Health Organ., EBL 43.65. 11 p. Cooley, R. A. 1928. Tick parasites. Montana State Bd. Ent. 7th Bien. Rept.: 10-16. Cooley, R. A. 1932. The Rocky Mountain wood tick. Montana Agric. Expt. Sta. Bull. 268. 58 p. Cooley, R. A. & G. M. Kohls. 1933. A summary on tick
parasites. 5th Pacific Sci. Cong.
Proc. 5: 3375-81. McMurtry, J. A.
1978. Acarina, Ixodidae. In: C. P. Clausen (ed.), Introduced Parasites
and Predators of Arthropod Pests and Weeds:
A world Review. U. S. Dept. Agriculture,
Agric. Handbk. No. 480. 545 p. Morton, F. A. 1928. Quantity production of tick
parasites. Montana State Bd. Ent. 7th
Bien. Rept.: 32-5 Smith, C. N. & M. M. Cole 1943. Studies of parasites of the American dog tick. J. Econ. Ent. 36: 569-72. Smith, C. N., M. M. Cole & H. K. Gouck. 1946.
Biology and control of the American dog tick. U. S. Dept. Agric. Tech. Bull. 905. 74 p. Wood, H. P. 1911. Notes on the life history of the tick
parasite, Hunterrellus hookeri How. J. Econ. Ent. 4: 425-31. |
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