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. 2015 Feb 22:8:117.
doi: 10.1186/s13071-015-0731-7.

Application of Polovodova's method for the determination of physiological age and relationship between the level of parity and infectivity of Plasmodium falciparum in Anopheles gambiae s.s, south-eastern Benin

Rodrigue Anagonou  1   2 , Fiacre Agossa  3   4 , Roseric Azondékon  5   6 , Marc Agbogan  7 , Fréderic Oké-Agbo  8   9 , Virgile Gnanguenon  10   11 , Kèfilath Badirou  12   13 , Ramziath Agbanrin-Youssouf  14   15 , Roseline Attolou  16   17 , Gil Germain Padonou  18   19 , Arthur Sovi  20   21 , Razaki Ossè  22   23 , Martin Akogbéto  24   25
Affiliations

Application of Polovodova's method for the determination of physiological age and relationship between the level of parity and infectivity of Plasmodium falciparum in Anopheles gambiae s.s, south-eastern Benin

Rodrigue Anagonou et al. Parasit Vectors. .

Abstract

Background: Polovodova method based on counting follicular dilatations estimates the number of egg-laying in mosquitoes. However, some researchers doubt the reliability of this method because of the absence of multiple dilatations in vectors after many gonotrophic cycles. It is in this context of controversy that our study was carried out to evaluate the importance of follicular dilatations in the determination of parity levels in An. gambiae s.s. Moreover, the application of this method allowed us to clarify the evolution of vectors' infectivity to P. falciparum according to their parity level.

Methods: We used two techniques to determine the parity level in An. gambiae s.s. We used two batches of wild strain mosquitoes reproduced after a known number of egg-laying in laboratory. The first batch was submitted to oil injection in the ovaries using a micropipette. In the same way, the classic technique of ovaries dilaceration (a technique based on the Polovodova method) was applied to the second batch. In order to assess relationship between parity level and mosquitoes' infectivity, Polovodova method was applied on vectors collected on humans. Finally, Heads and thoraces of these vectors were individually analyzed for P. falciparum antigen detection using an ELISA assay.

Results: In the first batch including 50 female mosquitoes "never laid", 50 "laid once", 50 "laid twice" and 48 "three times", oil injection technique revealed 42 nulliparous, 44 uniparous, 46 biparous and 44 triparous respectively. Overall, Polovodova method was effective using oil injection technique (p > 0.05). On the other hand, in the second batch that has a similar number of laying to the first batch, the application of Polovodova method through classical technique of ovaries dilaceration was ineffective with multiparous females (p < 0.05). Moreover, probability of vector infectivity increased with the number of egg-laying (p < 0.0001).

Conclusion: Our results revealed that the Polovodova method is reliable for estimating the number of egg-laying in Anopheles gambiae s.s. using oil injection technique in the ovaries. The study has also showed an increased likelihood of infectivity in vectors according to the number of egg-laying.

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Figures

Figure 1
Figure 1
The villages of Itassoumba (district of Ifangni) and Abomey-takplikpo (district of Adjarra) in South-Eastern Benin.
Figure 2
Figure 2
Ovariole devoid of dilatation observed from oil injection technic (Photo CREC, 2013).
Figure 3
Figure 3
Ovariole with one dilatation observed from oil injection technic (Photo CREC, 2013).
Figure 4
Figure 4
Ovariole with two dilatations observed from oil injection technic (Photo CREC, 2013).
Figure 5
Figure 5
Ovariole with three dilatations observed from oil injection technic (Photo CREC, 2013).
See this image and copyright information in PMC

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