Biology Reference
In-Depth Information
Disease Relationship
A total of 11 KFD virus isolations have been reported from the nymphal stages of
this species from KFD area during the period of 1961
1972. However, its role in
the KFD transmission cycle is still not known.
Parasitism of H. bispinosa Nymphs by a Hymenopteran Parasite
Hunterullus sagarensis
39,40,41
Parasitism of H. bispinosa nymphs by a chalcid parasite, H. sagarensis, has been
reported from many villages in Karnataka and Maharashtra states. Mass breeding
of H. bispinosa in cattle sheds in India is well known and the parasite had been
recorded from fed nymphs collected from these cattle sheds.
Out of a total of 59 villages searched, fed nymphs of H. bispinosa were col-
lected from 49 villages of Karnataka state. Of the 49 villages, 71.4% were positive
for the parasites. Rate of infestation of ticks ranged from 0.3% to as high as 48.9%.
The female chalcid alighted on the nymph and oviposited inside the body cavity
by piercing through the dorsal body wall with its stylets. Development of the para-
site starts only when the parasitized nymphs take a full blood meal. None of the
eggs showed any sign of development in unfed nymphs. Parasite larvae could be
dissected out from fed nymphs on the first day of their detachment from the host.
Five to ten days after detachment, the external symptom of parasitism could be
noticed in parasitized nymphs. The inner content could be seen eaten up partly in
the initial period and completely later on. The nymphs started dying from the sev-
enth day. Total developmental period from egg to adult, excluding the dormant
period in the unfed nymph, varied from 30 to 36 days under laboratory conditions.
The adults emerged from the nymphs by gnawing holes on the posterior aspects.
The immature stages completely destroyed the inner content of the tick and
only the exoskeleton was left. Usually, one to three parasites emerged from a single
nymph but in some cases as many as five were observed. The life span of adults
was very short, ranging from 2 to 4 days. Sex ratio of 1,020 chalcid parasites
emerged from 350 nymphs collected from the field showed that 384 were males
and 636 females, giving an approximate male-to-female ratio of 1: 1.6.
These chalcids have been collected in all the months of the year. Though there
is some difference in the percentage parasitism from month to month and between
two localities, it is not possible to attach any seasonal significance. However, there
was an apparent decline in the number of nymphs parasitized in the dry month of
April. The presence of the parasite throughout the year is apparently due to the
availability of a suitable host in all the seasons inside the cattle sheds.
8
Laboratory experiments on host range showed that in addition to the nymphs of
H. bispinosa,thoseofH. spinigera, H. turturis,andH. kinneari could be also parasit-
ized. However, it did not oviposit on the nymphs of B. microplus, which is also a com-
mon cattle tick of this area. The parasitized unfed nymphs were as active as the
nonparasitized ones until they were fully fed when the development of the chalcid
flies starts inside the body. Only the unfed nymphs were susceptible for the
parasitism.
