Stegomyia indices and pattern recognition of Aedes aegypti (Diptera: Culicidae) in selected agrogeoclimatic zones of Punjab, Pakistan.

Mosquito-borne diseases especially, dengue is gaining currency nowadays in Pakistan. As there is no approved dengue vaccine available worldwide, prevention and control of vector is the only solution amid prevailing circumstances. The present study is a maiden attempt to screen indoor and outdoor breeding containers for the presence of Aedes (Ae.) aegypti larvae from selected study districts of Punjab, Pakistan i.e., Dera Ghazi Khan (DG Khan), Chakwal, and Faisalabad. A total of 384 houses from each study districts were surveyed for a calendar year. Mosquito larvae were collected, preserved, and identified using standard taxonomic keys. House Index (HI), Container Index (CI), and Breteau Index (BI) were estimated. Chi-square analysis was applied to calculate the association between Ae. aegypti larvae and breeding containers. Chakwal was identified with the highest values of Stegomyia indices (HI = 46.61 %, BI = 91.67 %, and CI = 15.28 %) followed by Faisalabad (HI = 34.11 %, BI = 68.75 % and, CI = 13.04 %) and DG Khan (HI = 28.39 %, BI = 68.23 % and, CI = 11.29 %). Earthen jars, tree holes, and water tanks were found significantly (p < 0.05) associated with the abundance of larvae irrespective of the geographical location. However, flower tubs and plastic buckets were found significantly (p < 0.05) associated in Faisalabad and Chakwal while, tyres and plastic bottles were found associated (p < 0.05) with the abundance of Ae. aegypti larvae in Faisalabad and DG Khan. These findings will help the stakeholders to devise appropriate preventive measures in combating the risk of dengue transmission.

Mitigating the Public Health Issues Caused by the Filarial Vector, Culex quinquefasciatus (Diptera: Culicidae) Through Phytocontrol and Larval Source Marker Management.

Failure of conventional mosquito control strategies to curb the population of vectors have made the humans vulnerable to serious medical problems transmitted by them. This effect has been compounded by global climate change enabling the mosquitoes to cross geographical boundaries and cause trouble in regions where they were initially not found. As such, the scientific community has been compelled to devise alternative and innovative strategies of mosquito control that can be integrated with the conventional practices to implement multi-phasic approach of vector management. Culex quinquefasciatus is one such mosquito species that is reported to be one of the primary vectors of lymphatic filariasis and many other diseases of global health concern. However, not much is known about its breeding habitat ecology and microbial properties that have enabled the species to achieve reproductive success in urbanized habitats. The current investigation was carried out at Digha, West Bengal, India. The region, despite being endemic for lymphatic filariasis, has rarely been explored for its mosquito diversity and/or their breeding habitat characteristics. Therefore, these were attempted. For survey and sampling, seven villages were chosen, namely, Duttapur, Jatimati, Champabani, Padima, Gobindabasan, Bhagibaharampur and Palsandapur. The study showed that Cx. quinquefasciatus is the dominant mosquito species at the sampling sites with the highest density of their larvae being recorded from man-made structures like drains and pools close to human habitations and livestock. The study was, therefore, restricted to Cx. quinquefasciatus. Seasonal abundance showed that they were most prevalent in the monsoon followed by summer. The physicochemical characterization showed their larvae to prefer almost neutral pH (6.9 to 7.3), low chloride concentration (98 to 258 ppm) and turbidity. As far as other parameters are concerned, they were tolerant towards a wide range allowing them to adapt varied habitats in the study areas. The bacterial profiling of their natural habitat waters revealed the presence of Paenibacillus nanensis DGX1(OQ690670), Bacillus cereus DGX2(OQ690675), Bacillus sp. DGX3(OQ690700) and Escherichia coli DGX4(OQ690701). Bacillus cereus was found to have high oviposition attractant properties in oviposition assays. Bacillus cereus was also obtained from the midgut of third instar larvae indicating that they had entered from the surrounding medium and colonized the larval gut. Subsequent tests exhibited the roles of B. cereus in larval development. Numerous plant products have been reported either as insecticides for killing larvae or adult mosquitoes or as repellents for mosquito biting and the best alternatives for mosquito control. Larvicidal potential of emulsified neem oil formulation against the field collected 3rd instar larvae of Culex quinquefasciatus mosquito under laboratory conditions was also evaluated. The information thus obtained can be pooled to generate larval source markers and larval source management practices by altering their habitats that cannot be removed. Furthermore, the time of implementation of these strategies can also be planned.

Studies on the breeding potential and entomological indices of dengue vector Aedes aegypti and Aedes albopictus in the district Ghaziabad of Uttar Pradesh, India.

BACKGROUND & OBJECTIVES: The female Aedes mosquito is a vector of many arboviruses-borne diseases. The evidence and information regarding their breeding habitats are vital for implementing appropriate control policies. METHODS: An entomological survey was done at three sites in Ghaziabad district of Uttar Pradesh, India viz. Indirapuram, Vasundhara, and Vaishali to generate the first boundary line information of breeding sites of Aedes aegypti larvae for the early prevention and control interventions for dengue management. RESULTS: A total of 2994 containers were checked in 1169 households at the time of the survey for breeding sites of Aedes mosquito during the pre-monsoon, monsoon, and post-monsoon period, out of which 667 containers were found positive in 518 positive households. The total HI, CI, and BI were 44.31, 22.27, and 57.05 respectively. The maximum and minimum breeding indices were found during monsoon and pre-monsoon respectively. The most preferred containers for Aedes breeding were cement tanks for lotus plants in nurseries, drums, and small and large size pots for storage of water and ornamental plants mostly in 8 plant nurseries. INTERPRETATION & CONCLUSION: Breeding of Aedes was found in nurseries and desert coolers which were the primary breeding containers found during the survey. The containers found positive during surveys were emptied or destroyed with the help of the local community and the breeding status of nurseries was informed to the health authorities of Ghaziabad to take necessary action against the breeding sites of the Aedes mosquitoes.

Sex-related and spatial variation in trace elements in feathers of the Kentish plover (Charadrius alexandrinus) from different coastal areas of the Iberian Peninsula.

This study investigated the sex-related and spatial variation in trace elements concentrations in feathers of the Kentish plover (Charadrius alexandrinus) inhabiting different coastal locations in the Iberian Peninsula. Feathers were sampled in a total of 50 breeding birds from 7 different locations: 3 on the Mediterranean coast (n=18), 1 on the Atlantic coast of Andalusia (n=9) and 3 on the NW Atlantic coast (n=23). The feathers were analyzed to determine the concentrations of Al, Cr, Mn, Cu, Zn, As, Se, Cd, Hg and Pb. All of the trace elements were present at detectable concentrations, and the mean concentrations of Al, Zn and Cu were highest of those considered. The coastal section had a significant effect on 5 elements (Mn, Cu, As, Cd and Pb). The mean concentrations of almost all of the trace elements were highest in the birds from Andalusia, intermediate in the birds from the Mediterranean area and, in general, lowest in the birds from the NW Atlantic coast. Females showed significant higher Mn concentrations and high levels of exogenous elements (Al and As) in contrast with males. Less preening activity during the day of female birds, when they are occupied in incubating eggs, could favour higher concentrations of exogenous trace elements. The high levels of several trace elements observed in the samples from Mediterranean and Atlantic coast of Andalusia may pose a serious threat to these populations.

Entomological investigation of an outbreak of Japanese encephalitis in Solan district, Himachal Pradesh.

An outbreak of Japanese encephalitis (JE) was reported in Solan district of Himachal Pradesh, India in May 2018 wherein a total of eight JE cases were reported by the state health department, of which seven cases were confirmed by ELISA. An entomological survey was carried out to investigate the presence of vector mosquitoes in the affected area. Field visits were undertaken in eight villages of two blocks in Solan district. Larval collections were made from the major aquatic sites and emerging mosquito species were identified. Seepage water ditches were the main source of JE vector mosquitoes Culex tritaeniorhynchus and Cx. bitaeniorhynchus. During hand catch collections of adult mosquitoes, three vector species of JE,Culex tritaeniorhynchus (Man Hour Density 1-14), Cx. vishnui (MHD 2) and Cx. bitaeniorhynchus (MHD 1-2) were collected. A few specimens of Cx. tritaeniorhynchus (6 no.) were also collected in light trap collections. Since this was the first reported outbreak of JE from Himachal Pradesh, India, studies on sero-surveillance in addition to bionomics of JE vectors are required for better understanding of epidemiology of JE in Himachal Pradesh. Moreover, there is a need to study the role of climate change especially rising temperature in the context of JE in Himachal Pradesh.

Prevalence of dengue vectors, larval breeding habitats, Stegomyia indices and their correlation with dengue cases in urban and rural areas of Punjab, India.

BACKGROUND & OBJECTIVES: The state of Punjab, India is highly endemic for dengue fever as high number of confirmed dengue cases have been reported since 2013. A better understanding of vectors distribution and their seasonal variation is necessary to control the disease. Therefore, the present study was conducted in both rural and urban areas of 11 out of 22 districts of Punjab to highlight seasonal prevalence of Aedes vector mosquitoes. METHODS: Entomological surveys were carried out in different seasons and all kinds of indoor and outdoor breeding habitats were examined and Aedes immatures were collected. The Stegomyia indices were calculated and compared from urban and rural areas in different seasons. RESULTS: Both vectors of dengue, i.e. Aedes aegypti and Ae. albopictus were recorded to be prevalent. Ae. aegypti mosquitoes were observed in all districts surveyed while Ae. albopictus were found only in seven districts of Punjab. The Stegomyia indices were significantly high during monsoon as compared to pre- and post- monsoon periods. Occurrence of dengue cases were found to be correlated with the Stegomyia indices. INTERPRETATION & CONCLUSION: This is the first detailed study of prevalence of dengue mosquito vectors in Punjab showing the presence of Ae. aegypti and Ae. albopictus in both urban and rural areas of the state, thereby demonstrating wide distribution of this vector. Different breeding habitats identified in the study should be subjected to targeted intervention such as source reduction in order to achieve effective control of dengue cases.

Socio-demographic and household attributes may not necessarily influence malaria: evidence from a cross sectional study of households in an urban slum setting of Chennai, India.

BACKGROUND: Household and environmental factors are reported to influence the malaria endemicity of a place. Hence, a careful assessment of these factors would, potentially help in locating the possible areas under risk to plan and adopt the most suitable and appropriate malaria control strategies. METHODS: A cross-sectional household survey was carried out in the study site, Besant Nagar, Chennai, through random sampling method from February 2014 to February 2015. A structured interviewer-administered questionnaire was used to assess selected variables of demography, structural particulars of a household, usage of repellents, animals on site, presence of breeding habitats and any mosquito/vector breeding in the household, malaria/vector control measures undertaken by government in each houses. The data was collected through one to one personal interview method, statistically analysed overall and compared between the households/people infected with malaria within a period of 1 year and their non-infected counterparts of the same area. RESULTS: Presence of malaria was found to be significantly associated with the occupation, number of inhabitants, presence of a separate kitchen, availability of overhead tanks and cisterns, immatures of vector mosquitoes, presence of mosquito breeding and type of roof structures (p < 0.05). However, age, gender, usage of repellents, animals on site, number of breeding habitats or detection of vector breeding did not significantly associate with the malaria incidence/prevalence. CONCLUSIONS: The survey revealed various demographic, household and environmental factors likely to associate with the malaria incidence/prevalence in an urban slum of Chennai. The socio-demographic and household variables have revealed disparities in malaria infection from the present cross sectional study. The absence of significant association with many parameters indicates the probable role of other confounding factors which influence the malaria prevalence.

Does fluoride influence oviposition of Anopheles stephensi in stored water habitats in an urban setting?

BACKGROUND: The physico-chemical characteristics of lentic aquatic habitats greatly influence mosquito species in selecting suitable oviposition sites; immature development, pupation and adult emergence, therefore are considerations for their preferred ecological niche. Correlating water quality parameters with mosquito breeding, as well as immature vector density, are useful for vector control operations in identifying and targeting potential breeding habitats. METHODS: A total of 40 known habitats of Anopheles stephensi, randomly selected based on a vector survey in parallel, were inspected for the physical and chemical nature of the aquatic environment. Water samples were collected four times during 2013, representing four seasons (i.e., ten habitats per season). The physico-chemical variables and mosquito breeding were statistically analysed to find their correlation with immature density of An. stephensi and also co-inhabitation with other mosquito species. RESULTS: Anopheles stephensi prefer water with low nitrite content and high phosphate content. Parameters such as total dissolved solids, electrical conductivity, total hardness, chloride, fluoride and sulfate had a positive correlation in habitats with any mosquito species breeding (p < 0.05) and also in habitats with An. stephensi alone breeding. Fluoride was observed to have a strong positive correlation with immature density of An. stephensi in both overhead tanks and wells. CONCLUSION: Knowledge of larval ecology of vector mosquitoes is a key factor in risk assessment and for implementing appropriate and sustainable vector control operations. The presence of fluoride in potential breeding habitats and a strong positive correlation with An. stephensi immature density is useful information, as fluoride can be considered an indicator/predictor of vector breeding. Effective larval source management can be focussed on specified habitats in vulnerable areas to reduce vector abundance and malaria transmission.

Dengue vectors in urban and suburban Assam, India: entomological observations

Background: Dengue is rapidly becoming established in north-east India andspreading, on account of rapid urbanization and population movement, withreported morbidity and attributable death cases. This study aims to determine theseasonal abundance of Aedes (Stegomyia) albopictus and Aedes (Stegomyia)aegypti in Guwahati metropolis and suburban settlements; to characterize thebreeding resources for these mosquitoes; and to ascertain the status of theirsusceptibility to adulticides and larvicides.Methods: Mosquito larval surveys were carried out in different localities in bothGuwahati city and adjoining suburbs from January to December 2013, to determinethe seasonal abundance of disease vectors and their breeding preferences.The insecticide susceptibility status of mosquito adults and larval populations ofboth Aedes aegypti and Aedes albopictus was ascertained, using World HealthOrganization standard diagnostic concentrations and test procedures.Results: The study revealed that both Aedes aegypti and Aedes albopictus arewidely abundant in Guwahati city and suburbs, and breeding in a wide variety ofresources. Aedes albopictus, however, was the predominant mosquito speciesin suburbs, breeding preferentially in flower vases, cut-bamboo stumps and leafaxils. Aedes aegypti was the most common in the city, breeding predominantly indiscarded tyres, cement tanks and used battery boxes. Both Aedes aegypti andAedes albopictus were resistant to dichlorodiphenyltrichloroethane (DDT; 4%), butsusceptible to malathion (5%), and exhibited a varied response to pyrethroids.However, larval populations of both these mosquito species were susceptible tolarvicides, including malathion (1.0 mg/L), temephos (0.02 mg/L) and fenthion(0.05 mg/L), at much lower dosages than diagnostic concentrations.Conclusion: Given the seasonal abundance and case incidence in city areas,it is highly probable that Aedes aegypti is the predominant mosquito vectortransmitting dengue virus. The study results have direct relevance for the statedengue-control programme, for targeting interventions and averting outbreaks andspread of disease

Studies on breeding habitats and density of postembryonic immature filarial vector in a filarial endemic area

Objective: To obtain a complete and systematic data about the breeding habitats and density of vector immatures (larvae & pupae) in a filarial endemic area. Methods: All the possible permanent and temporary water bodies were surveyed systematically. Four hundred samples were taken in each season from each type of habitats. Sampling was done with a 250 mL dipper and immature mosquitoes were identified following standard keys. Results: In summer, rainy and winter seasons, overall 49.64%, 44.64%, and 28.57% of the habitats were positive for immature filarial vector (Culex quinquefasciatus) respectively; 36.93%, 35.11%, and 21.18%of the samples were positive for immatures respectively and overall per dip densities (PDD) of them were 10.29, 10.18, and 4.40 respectively. In the study year overall PDD were much higher in open cesspits (19.53) and drains (17.24) than in other habitats. Peak PDD of vector immatures in Dobas (ditches), open cesspits and drains were in March whereas in paddy fields and temporary water bodies peak PPD were in September. Conclusion: Dobas, paddy fields, open cesspits, drains, and temporary water bodies were found to be the main breeding sites of filarial vector, Cx. quinquefasciatus in different months. Open cesspits and drains were suitable almost throughout the year with peak in summer. Dobas also act as a steady breeding site throughout the year, whereas temporary water bodies immerge as strong breeding site during pre-monsoon and monsoon seasons. Information about the breeding habitats will be helpful to formulate a filarial vector control strategy and in turn to control the filarial diseases in the study area.