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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 94, Num. 4, 1999, pp. 575-576
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OC99105
Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 94(4),Jul./Aug.
1999: pp 575-576
RESEARCH NOTE: Development of
Dirofilaria immitis (Leidy) in Aedes aegypti (L.)
and Culex quinquefasciatus (Say) from
Maceió, Alagoas, Brazil
Ana C Brito/+, Gilberto Fontes,
Eliana MM da Rocha, Deisy AM Rocha, Lêda Regis*
Departamento de Patologia, Centro de Ciências
Biológicas, Universidade Federal de Alagoas, Praça
Afrânio Jorge s/no, 57010-020
Maceió, AL, Brasil *Departamento de Entomologia, Centro de
Pesquisas Aggeu Magalhães-Fiocruz, Recife, PE, Brasil
+Corresponding author. Fax: +55-82-221.2501. E-mail: acbs@fapeal.br
Received 24 September 1998 , Accepted 22 March 1999
Code Number:OC99105
RESEARCH NOTE
Dirofilaria immitis (Leidy, 1856) is a
nematode that can be transmitted mainly by mosquitoes of the genera
Aedes, Culex and Anopheles (KW Ludlam et al. 1970
JAVMA 157: 1354-1359). The susceptibility of mosquitoes to
support development of D. immitis not only differs according
to the vector species but also with regard to strains of a
particular species (BM Christensen et al. 1984 J Invertebr
Pathol 44: 267-274, CSB Apperson et al. 1989 J Am Mosq
Control Assoc 5: 377-382). A recent survey carried out in
Maceió, State of Alagoas, Brazil, showed a prevalence rate
of 3% of canine filariasis (unpublished data), but the local vector
of D. immitis has not yet been determined. The occurrence of
Ae. scapularis, Cx. nigripalpus and Mansonia
titillans mosquitoes has been reported in Maceió (CML
Calheiros 1996 Transmissores em Potencial e Naturalmente
Infectados pela Wuchereria bancrofti (Cobbold, 1877) em
Maceió- Alagoas, MSc Thesis, UFMG, 147 pp.).
However, Cx. quinquefasciatus and Ae. aegypti,
the local vectors of bancroftian filariasis and dengue fever
respectively, are the most abundant mosquito species in
Maceió. Results of experiments carried out to demonstrate
the susceptibility of these species to infection with D.
immitis and their vector efficiency are reported here.
Key words: Dirofilaria immitis - heartworm -
Aedes aegypti - Culex quinquefasciatus
Both mosquitos populations were originated from
Maceió. Therefore, Ae. aegypti were reared at
the insectary of Fiocruz, Recife, PE and the strain of
Cx. quinquefasciatus was maintained at the insectary of
the Universidade Federal de Alagoas in Maceió. Mosquitoes
eggs were hatched in cubes containing dechlorinated water, larvae
were reared with cat food (WhiskasÒ) and adults
were kept at 27±1ºC and 70±10% R.H. A 4 years-old mixed-breed male
dog naturally infected with D. immitis was used as the
microfilariae (mf) donor (80 mf/20 ml blood) and one uninfected
animal was used as control. Females 3-to 7-day-old of both mosquito
species were allowed to feed on blood with anticoagulant via an
artificial apparatus (LC Rutledge et al. 1964 Mosq News
24: 407-419) or directly on microfilaraemic and
amicrofilaraemic dogs. Four different experiments were carried out
and both mosquito species were fed simultaneously on the dog and
via artificial apparatus between 4 p.m. and 5 p.m., during 30 min.
Mosquitoes were dissected daily and D. immitis larvae
were recorded. The developmental stages of the parasite were
identified according to AER Taylor (1960 J Helminthol 34:
27-39). Mortality was recorded daily and the vector efficiency of
mosquito species was determined as described by L Kartman (1954
Exp Parasitol 2: 27-78).
Survival rates recorded with a total of 1,573
Cx. quinquefasciatus and 1,588 Ae. aegypti
females fed on the microfilaraemic dog, were 30.6% and 20%
respectively. For mosquitoes fed on the uninfected dog the values
were 85% for the former and 46.4% for the latter species. The death
of infected mosquitoes could be caused by the movement of large
numbers of mf from the midgut to the Malpighian tubules as
suggested by DR Hamilton and RE Bradley (1979 J Med Entomol
3: 305-306). The sausage form was observed on the 4th day and
from days 8 to 9, the larvae grew longer and more narrow
(L2) reaching the infective larval stage (L3)
on the 10th day for Ae. aegypti and four days later for
Cx. quinquefasciatus. Shorter developmental periods of
D. immitis in a vector, as observed in
Ae. aegypti, would favour disease transmission (KM
Loftin et al. 1995 J Am Mosq Control Assoc 11: 90-93).
Although both mosquito species ingested similar number of mf, the
number of L3 recorded per female was significantly
higher in Ae. aegypti. In fact, no L3 were
recorded in Cx. quinquefasciatus which fed directly on
the microfilaraemic dog and only one L3 was recorded in
females which fed using the apparatus. In both species a large
number of L3 parasite larvae was produced when females
were fed through the apparatus (Table).
The overall vector efficiency of Ae. aegypti was
seven times higher than that of Cx. quinquefasciatus.
According to Loftin et al. (1995 loc. cit.), the vector
efficiency in Cx. quinquefasciatus was 2.7% compared with
20.4% of Ae. vexans. RC Lowrie (1991 J Am Mosq Control
Assoc 7: 30-36) observed that the efficiency of Ae.
taeniorhynchus was 65 times higher than that of Cx.
quinquefasciatus. In conclusion, our results demonstrate that
local populations of both mosquito species are susceptible to D.
immitis allowing larval evolution until the L3 stage
and that Ae. aegypti has clearly better potential
than Cx. quinquefasciatus as a vector of canine
heartworm in Maceió. In this context,
Cx. quin-quefasciatus has been considered as a poor
vector of D. immits in different regions (N
Labarthe et al. 1998 Mem Inst Oswaldo Cruz 93: 425-432,
Lowrie 1991 loc. cit.). Investigations are being conducted
to identify mosquitoes naturally infected among species from
Maceió, by polymerase chain reaction using primers
species-specific for D. immitis.
Copyright 1999 Fundacao Oswaldo Cruz - Fiocruz
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