Prevalence of dengue and diversity of cultivable bacteria in vector
Aedes aegypti (L.) from two dengue endemic districts, Kanchanpur and
Parsa of Nepal
Background: Dengue fever, an endemic arboviral disease, represents one
of the major public health concerns in Nepal. It is transmitted by
bites of infected Aedes aegypti and Aedes albopictus , the former
being primary vector. The bacterial community plays a significant role
in biology of mosquitoes; however, the bacterial communities of primary
vector A. aegypti remain unstudied in Nepal. The study was designed to
determine the rate of dengue seropositivity and to explore the
bacterial diversity of A. aegypti from dengue endemic districts,
Kanchanpur and Parsa of Nepal. Methods: A cross-sectional study was
conducted between June 2013 and November 2013 at two hospitals of
Kanchanpur and Parsa. A total of 221 serum samples were collected from
patients (inpatients and outpatients) suspected of suffering from
dengue fever and attending Mahakali Zonal Hospital, Mahendranagar,
Kanchanpur, and Narayani Zonal Hospital, Birgunj, Parsa. Detection of
anti-dengue IgM was performed by using human dengue IgM capture ELISA.
The larvae and pupae of mosquitoes (A. aegypti) were collected, reared,
and emerged. Then, the bacteria were isolated and identified from the
gut of identified mosquitoes by using standard methods. Results: Out of
total 221 serum samples collected from patients suspected of suffering
from dengue fever, 34 (15.38%) were positive for anti-dengue IgM.
Gram-negative bacteria were isolated in largest proportion (63%)
followed by gram-positive cocci (23.27%) and gram-positive rods
(13.73%). The most common cultivable bacteria isolated were
Staphylococcus spp., Pseudomonas spp., and Acinetobacter spp. The
average bacterial load in the vectors was 3.91
7 104 cfu/ml.
Conclusions: High rate of anti-dengue IgM seropositivity was reported
in our study. The environmental bacteria were predominantly isolated
and identified in A. aegypti. The paratransgenic approach to control
vector might be possible by spreading the genetically modified bacteria
in larval habitat or shelter of adult mosquitoes