Abstract:
Mosquitoes transmit several diseases to humans. The blood feeding behaviour
of the mosquito and its ability to transmit pathogens in the course of blood-feeding
are important aspects in the epidemiology of vector-borne diseases. Multiple blood
feeding was observed within a single gonotrophic cycle in a laboratory colony of
Anopheles tessellatus Theobald. Sugar feeding on either glucose or sucrose did not
influence the longevity of adults from the colony. Adult An. tessellatus derived from
larvae reared under different conditions of crowding showed differences in body size
and body reserves i.e., carbohydrates, lipids, and proteins. Mosquitoes that resulted
from larvae reared in uncrowded conditions were larger than those that resulted from
larvae reared under crowded conditions. A large proportion of small mosquitoes
required more than one blood meal in single gonotrophic cyc!e compared to
mosquitoes of larger size. The fecundity and blood meal size were affected by the
size of the mosquito.
Antimosquito antibodies were raised in rabbits and mice against mosquito
antigens derived from the head/thorax, midgut, and abdomen tissues. Antigens
derived from sugar-fed mosquitoes were used for immunising rabbits and antigens
derived from blood-fed mosquitoes were used to raise antibodies in mice. Murine
antibodies to brain tissue of blood-fed An. tessellatus were also produced. The effects
of these antibodies on the longevity and fecundity of An. tessellatus and Culex
quinquefasciatus Say were investigated. Rabbit antimosquito antibodies reduced the
fecundity of An. tessellatus and the longevity of Cx. quinquefasciatus. Murine
antimosquito antibodies reduced the fecundity of An. tessellatus. Murine antibodies
to brain tissue of blood-fed An..tessellatus when ingested in a blood meal did not
influence mosquito mortality and fecundity. It is postulated that antibodies against
antigens shared among the head/thorax, midgut, and abdomen tissues are involved in
the reduction of fecundity. It is also shown by ultrastructural studies that rabbit
antibodies to midgut tissue of An. tessellatus inhibited the formation of the peritrophic
membrane in the posterior region of the An. tessellatus midgut.
The susceptibility of An. tessellatus to Plasmodium vivax Grassi was reduced
when mosquitoes ingested P. vivax gametocytes in human erythrocytes suspended in
rabbit sera containing antiAn. tessellatus antibodies. In the presence of antimosquito
antibodies, fewer oocysts of P. vivax developed in the mosquito midgut. This
reduction in the infectivity of P. vivax to An. tessellatus was independent of
complement. A second blood meal containing antimidgut antibodies, given 48 or 72
hours after the infective blood meal, did not enhance the transmission blocking effect.
Immunoglobulin (IgG) purified from antimidgut sera was shown to mediate the
transmission blocking effect.
Monoclonal antibodies (MAbs) to antigens derived from the midgut of An.
tessellatus did not affect the mortality and fecundity of An. tessellatus when these
MAbs were fed to mosquitoes either in an in vitro blood feed, or vy direct feeding
of mosquitoes on mice producing ascites. The infectivity of P. vivax to An. tessellatus
was also not influenced by an infective blood meal containing these MAbs.