Histomorohological Studies on Ovary of Guppy (Poecilia Reticulata) And Development of Follicular Placenta

The larvivorous fish Poecilia reticulata was propagated prolifically in the garden for control of mosquito vectors and later redistributed in a number of water reservoirs, in different villages nearby Dapoli. The gravid live bearing females were quickly dissected for their ovaries and embryos. The developed embryo with yellow rounded yolk sac, the remnants of the follicular placental tissue and thick vascular network of connective tissue was also observed.

Field Efficacy of Larvivorous Fish and Pyriproxyfen Combined with Community Engagement on Dengue Vectors in Cambodia: A Randomized Controlled Trial

Evidence on the effectiveness of low-cost, sustainable biological vector control tools for Aedes mosquitoes is limited. Therefore, the purpose of this trial was to estimate the impact of guppy fish in combination with the larvicide pyriproxyfen (PPF) (Sumilarv® 2MR) and communication for behavioral impact (COMBI) activities to reduce entomological indices in Cambodia. In this cluster randomized, controlled superiority trial, 30 clusters comprised of one or more villages each was allocated in a 1:1:1 ratio to receive either 1) all three interventions (guppies, PPF, and COMBI), 2) two interventions (guppies and COMBI), or 3) control (standard vector control). Entomological surveys among 40 randomly selected households per cluster were carried out quarterly. The primary outcome was the population abundance of adult female Aedes mosquitoes trapped using adult resting collections. In the primary analysis, adult female Aedes abundance and mosquito infection rates was aggregated over follow-up time points to give a single rate per cluster. These data were analyzed by negative binomial regression, yielding abundance ratios (ARs). The number of Aedes females was reduced roughly by half compared with the control in both the guppy, PPF, and COMBI arm (AR = 0.54; 95% CI, 0.34–0.85; P = 0.0073); and the guppy and COMBI arm (AR = 0.49; 95% CI, 0.31–0.77; P = 0.0021). The effectiveness demonstrated and extremely low cost of including fish rearing in community-based health structures suggest they should be considered as a vector control tool as long as the benefits outweigh any potential environmental concerns. Sumilarv® 2MR was also highly accepted and preferred over current vector control tools used in Cambodia.

Fish-Released Kairomones Affect Mosquito Oviposition and Larval Life History

Several species of mosquitoes respond to the presence of kairomones released by larvivorous predators during oviposition habitat selection and larval development. These responses may differ among mosquito species and do not always correlate with larval survival. This study examined the responses of the mosquito Culiseta longiareolata Macquart (Diptera: Culicidae) to kairomones released by three species of fish, Gambusia affinis (Cyprinodontiformes: Poeciliidae), Aphanius mento (Cyprinodontiformes: Cyprinodontidae) and Garra rufa (Cypriniformes: Cyprinidae) during oviposition. In addition, the study examined the effects of kairomones released by Gm. affinis on larval development and survival. Results show that ovipositing female avoided cues from the two larvivorous fish species but not the algivorous Gr. rufa. In addition, developing larvae metamorphosed slower and showed increased mortality when exposed to fish-released kairomones. Culiseta longiareolata larvae are known as dominant competitors, and the straightforward responses of both larvae and adult female to fish-released kairomones may be explained by the lack of additional sources of larval stress other than the presence of predators.

Current prevention and potential treatment options for dengue infection

Currently, treatments for dengue infection are only symptomatic as no antiviral agents nor vaccines are available to combat this virus. Despite challenges faced by researchers, many efforts are ongoing to reduce cases of dengue infection either by targeting the vector or the virus. Vector population is monitored and reduced by using mechanical, chemical and biological controls. Chemical control is achieved either by using synthetic or natural insecticides where the latter is more preferable. In biological control, bacteria, fungi and larvivorous fish are utilised to reduce the vector population. Moreover, genes of mosquitoes are also explored to produce progenies which are sterile with low survival ability. Vaccines are among the most effective ways to prevent viral infection. Various approaches have been used and are still being explored towards producing vaccines for dengue. These include live attenuated, inactivated, recombinant subunit, nucleic acid and virus-like particles vaccines. The aim is to produce a vaccine which can target all the four serotypes of the virus. Monoclonal antibodies are widely researched on to equip the host defense mechanism against the dengue virus. Deeper understanding of the virus replication cycle warrants the development of antiviral agents which target viral proteins vital for the replication process. Bioactive compounds are also utilised in the development of antiviral agents. The importance of surveillance and supportive therapy are also discussed.

The Influence of Digestive Tract Length of Larvivorous Fish Related to Predation Potential on Aedes aegypti Larvae

Biological vector control by using larvivorous fish will be beneficial in reducing Aedes aegypti population, hence reducing risk of dengue virus transmission. It is important to select the larvivorous fish according to its digestive organ.Current study aimed to investigate the predation potential among the fish species and to identify the influence of the digestive tract length of the fish related to their predation potential. The research was an analytical observational study with post-test only design. Third stage larvae of Aedes aegypti were used as preys for tilapia (Oreochromis niloticus), common carper (Cyprinus carpio), and guppy (Poecillia reticulata). In association with their digestive tract length, predation potential of tilapia, common carper, and guppy showed statistical differences (P<0.05). Tilapia demonstrated highest predation of the larvae, followed by common carper and guppy. There are associations between difference in shapes of mouth and intestines, mouth width, intestinal length, and predation potential of these fish species. Current study results showed possible associations between digestive tract length of tilapia, common carper and guppy and predation potential on Aedes aegypti larvae, allowing these fish species to be used inbiological control of Aedes aegypti.

A narrative review of the control of mosquitoes by Larvivorous fish in Iran and the world

Background and purpose: Mosquitoes are responsible for the transmission of many pathogens such as malaria, yellow fever, dengue fever, and so on. The control of mosquitoes using chemical insecticides is not always a sensible approach, so, alternative biological control methods, especially the use of larvivorous fishes, can play a significant role in controlling of mosquito larvae. Materials and Methods: In this narrative review study, papers and dissertations were collected without time and language limits from international electronic databases in Google Scholar, PubMed, ScienceDirect, Web of Science, Ovid, Medline and WHO site, and Iranian scientific databases including: Barakatkns, SID, Civilica, Magiran, and Medlib using appropriate keywords from 1937 to 2018. Finally, 55 sources were selected and criticized, interpreted, and analyzed. Results: In the study, some of larvivorous fishes including Aphanius dispar, Carassius auratus (goldfish), Gambusia affinis, and Poecilia reticulate (guppy) have been investigated as important predators of mosquito larvae. Among these fish, Gambusia, Aphanius dispar, Colisa Lalia, Danio rerio, Goldfish, Guppy and Oreochromis mossambica are present in different regions of Iran. Conclusion: Given the fact that malaria carriers are present in many regions of Iran and the climate of Iran is also potentially suitable for the transmission of malaria, it is recommended to use larvivorous fishes that are compatible with the environmental conditions of each area.

Biological Control of Mosquito Vectors

The main purpose of this review paper is to study different biological control methods for controlling mosquito vectors. Mosquitoes act as vector for many harmful diseases including malaria, dengue fever, yellow fever, filarial, encephalitis, chikungunya, dengue and poly arthritis. The use of chemical insecticides for controlling mosquitoes is limited because they develop resistance against these insecticides. So, efforts have been made to control the mosquito vectors by eco-friendly techniques. At present, biocontrol agents are used to control the mosquito species with the aim to reduce the impact and cost of insecticide based strategies. These biocontrol agents involve the use of natural enemies including bacteria, fungi, larvivorous fish, protozoans and nematodes. These agents target mosquitoes at different stages of their life cycle. In this paper, we focus on several bio-controlling methods used to reduce the population of mosquito vectors.