Roduction of Specific Antisera Against Selected Mammals and Identification of Blood Meals of Phiembotamine Sandjlies Transmitting Visceral Leishmaniasis (VL) in Ethiopia
No Thumbnail Available
Date
1999
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa, Ethiopia
Abstract
In an auempt to know the feeding preferences of phlebotomine sandflies that transmit
visceral leishmaniasis (VL) in Eth iopia, Phlebotomus mani"i and P. orielllaiis. and thus
to poilll to the possible reservoir host(s) of the disease in the country, blood meals of
the vectors were identified using the counter current immunoelectrophoresis (CCIE)
technique. First, genus/species-specific antisera were raised against the immunoglobulin
G (lgG) of ten potential hosts of the sand fly vectors: human, sheep, goat, donkey ,
horse, camel, cattle, squirrel, mongoose and hyrax. The IgG was fractionated from the
whole sera of the mammals by the ammonium sulphate precipitation method followed
by the ion-exchange chromatography technique. The antisera were developed by
prim ing (subcutaneously) rabbits, in triplicates, with water-in-oil emulsion of equal
volumes of IgG and Freund's Complete Adjuvant and then boosting with Freund 's
Incomplete Adjuvant. The potency of the ant isera was determined by assay ing each lest
bleed from each rabbit againstlhe homologous IgG. Cross-reactiv ities were checked by
screening each test bleed against heterologous IgGs. Human whole serum and IgG were
cross-reacted with anti-cattle antisera and vice versa. All other antisera were specific.
The titre of each test bleed was qualitatively determined by visualizing the
conspicuousness of the precipitin line. Hyperimmune antisera were used in blood meal
analysis. Eight blood meal samples (5 SergelJlomyia spp. and 3 P. manilll) were
collected , by sticky and CDC light traps, from Aba-Roba in a total of 42 night catches.
One hundred and six blood meal samples (94 P. orielJlalis and 12 P. bergerofl)
collected, by CDC, from the Middle Awash va lley and stored for about 4 years were
used. Each blood meal sample was tested against cortlmercial anti-dog and anti-rat IgGs
vi
in addition to the 10 ami-host sera raised in the present study. Of 114 blood meals
processed, hosts were identified for the 93 (8 1.6%): 2 P. martilli, 79 P. oriellfalis and
all P. bergeroli. None of Sergelllomyia blood meals were identified. 37.6% of the blood
meals detected were from single host sources: 20 from cattle, 10 camel, 2 squirrel , I
donkey, I human and I from mongoose. The rest 62.4% was from mixed sources.
Altogether, 80.6% of the meals identified were from caule origin and 59% from camel,
singly or in combination with OIher hosts. Thus. P. oriellfatis appears to be an
opportunistic feeder with a preference for cattle and camel at least in the Middle Awash
where these hosts occur in large numbers. The CCIE technique is specific and sensi tive
enough not only to detect mixed blood meals from close ly related hosts but halfdigested
meals. The assay is technically simple and inexpensive in terms of reagents
required. Thus, CCIE is a robust technique for identification of blood meals of
haemalophagous insect vectors in general and smaller nies such as phlebotomine
sandfl ies and of biting midges in particular.