Study designs.

Of the 11 studies, seven were Intervention Control studies[16,17,18,19,20,21,23] and four had Before-and-After studies design [13,14,15,22] (Table 1 for more detailed description).

Outcome measures.

In most studies, the classical immature entomological indices such as the House Index [16,22,23], Container Index[13,15,16,18,19,22,23]and Breteau Index [16,19,22,23] were used to measure the outcomes. Pupae/Person Index [13,23] and adult mosquito density [16,18,19] were also measured. Reduction of breeding sites [14] and positive ovitraps were also measured [14,19,20,22,23]. Mean number of (total, late and early stage) Aedes larvae[13,17,19,20], % prevalence of Aedes[20]and mean % reduction of Ae.albopictus[21] were some of the other outcome measures that were analysed. Other findings such as quantity of temephos, labour and time required for its application were analysed only in study number[19].

Factors affecting the residual efficacy of temephos (such as temperature, organic debris, exposure to sunlight, water use patterns, maintenance of water storage containers) and level of acceptance or resistance to use of temephos among household residents were analysed only in one study [15], and expenditure for temephos application was calculated only in study number[19]. Study number [13] was the only study that analysed the association between larval mortality and factors such as the mode of application of temephos using spoons or zip-lock bags, different water types, effects of sunlight and type of containers used for water storage.

Interventions.

The 11 studies had different temephos application periodicity, with four studies [14,16,20,23] conducted according to the dry and wet seasons while study number[23]applied temephos as a pre-seasonal focal treatment. Of the 11 included studies, five had used temephos in the form of sand granules [13,17,18,19,22], while study number [15] experimented with temephos zeolite formulations. Four of the studies [14,16, 20,23] did not mention the type of formulation and only mentioned the dose (as parts per million (10−⁶ or ppm), and in study number [21] different dosages of temephos were compared. In most of these studies, temephos was applied at a dose of 1 ppm based on the size of the containers [18,19]. However, in study number [23], temephos was applied based on the actual volume of water present at the time of inspection rather than the total holding volume of the containers. The mode of temephos application differed across studies and included such diverse methods as the use of permeable zip-lock bags [13], plastic spoons [19], granules placed in a well-perforated plastic micro-centrifuge tube that allowed the granules to be removed during monitoring procedures [20], corncob grit granules [21] and the application of wettable powder to walls[22]. In studies where temephos was compared to other insecticides [17,20], it was often compared to Spinosad [17,20] and Bti[20].

Sources of water and the container material also differed across studies. Study number [13] compared the effects of temephos in rain water, piped water or both and also its effects in fibrocement or plastic containers. Studies number [18,19] applied temephos in water which was not used for the purpose of drinking.

Community-effectiveness.

All 11 studies reported a post-intervention reduction in the immature stages when compared to their respective control group. It was observed that the treated sources were free of larvae for a variable period of time depending on the season of application [16,20,23], number of applications [14,19], dosage of temephos[21], procedure of control [19], and method of application with respect to the source of water and container for storage of water [13].

For example, it was observed in study number [16] that the Aedes population was effectively controlled for 4–8 weeks in the dry season with no larvae and 6–12 weeks in wet season. In study number [20], there was an absolute inhibition of mosquito development for 6–9 weeks in the dry season and 9 weeks in the wet season. However, study [24] showed a pre-seasonal focal treatment before the rains reduced indices for 9–11 weeks, after which they returned to pre-treatment levels.

When considering the number of applications, study[14] reported that as the number of applications increased to five, it led to the elimination of the immature population. Study[19]found that a total of four applications could be effective at suppressing entomological indices, but concluded that two treatments would most likely be effective if applied just before the rainy season and repeated again within 2 months.

Variable effectiveness of temephos according to dosage was reported in study number [21], when it was applied at half the maximum allowable dose (11.21kg AI/ha)it provided100% protection for 5 months, with excellent control at rates as low as 0.56kg AI/ha(100% reduction sustained for 8 weeks). Study number[17] reported 100% effectiveness for 90 days when temephos was applied at the dose of 20g/200 litres of water.

Study number [19] observed that cyclic mass treatment with temephos required a greater amount of larvicide, while the targeting of treatment to positive containers required a greater number of man-hours. The effective control period was 2.5 to 5 months with an average of 3 months. The study concluded that a combined method of cyclic mass treatment at 3 month intervals with simultaneous treatment of new habitats between the mass treatments would offer the best control.

Factors such as temperature, organic debris, and ultraviolet light from sunlight that possibly degraded the active compound were investigated in study numbered [15]. These factors coupled with rapid water use, draining, and refilling of containers shortened the residual effectiveness of temephos [15]. This study also pointed out that other factors such as regular supply and budget allocation for the purchase of temephos are major factors affecting the success of a programme. Likewise, in study number[13], the median duration of the temephos effect was two to three weeks, with the duration of the residuality affected by water management practices (water type and water turnover), which were found to be significantly associated with reduced larval mortality. This same study found that temephos applied inside zip-lock bags provided longer residual activity as compared to spoon based applications[13].

Study number[22] illustrated the community-effectiveness of temephos by eliminating Ae. aegypti from an island by applying temephos intensely as both a residual insecticide on walls of houses as well as the treatment of breeding sites. Through this combination of temephos treatments, Ae. aegypti was eliminated within 15 months of the implementation of the campaign.

Acceptability.

Very few studies evaluated the acceptability of temephos applications[13,15]. As per study [13], acceptability of householders for temephos application via zip-lock bags was higher than spoon based application since it was easy to apply and inexpensive to implement. In study [15], 89% of the participants refused to use temephos sand granules due to the unpleasant odour and increase in water turbidity and perceived safety risk. No studies analysed the operational challenges associated with temephos application or the undesirable consequences caused by it.

Study designs.

Of 16 studies in this group, nine were Before-and-After studies [24,26,27,31, 34,35,36,37,38], four Intervention Control Studies [25,28,30,32] and three Cluster Randomised Trials [29,33,39].All 16 studies used households as the sampling unit for the application of temephos in various domestic breeding sites. Two studies were conducted on islands [31,35], seven in cities or towns[26, 27,29,30, 33,38,39], three in villages [28,34,37], two in both rural and urban areas [24, 36] and for two studies, no description of the study site was available[25, 32] (Table 2 for more detailed description).

Interventions.

Of the four Intervention Control Studies [25, 28, 30, 32], no interventions were applied in the control group of one study [28]. Ultra low volume (ULV) pyrethroid thermal fogging [25], Bti and Methoprene-S [30] and 4% Malathion fog [32] were applied in the control groups of the other three Intervention Control studies. Among the three Cluster Randomised Trials [29,33,39], two studies [29, 39] used temephos in combination with other interventions as a control group for a different intervention under study. Health education with source reduction was applied in the control group of the third cluster randomised trial[33].

Sample size was highly variable, with the number of containers or premises varying from 235 [24] to the coverage of entire islands[30, 31, 35].Follow up periods ranged from 6months [28] to 9 years [34] post intervention. Only one study [25] used a parameter for dengue transmission (DHF), measuring in communities the basic knowledge of dengue in relation to previous occurrence of DHF cases.

Temephos application was most commonly combined with health education and information, education and communication (IEC) activities [24,27,38,33, 34,36,37,38,39], and three studies [27,38, 39]included the use of mass media. Environmental management [24,27,29,30,33, 34,39] and malathion adulticide applications[26,32,35,37,38] were also used in combination with temephos. Four studies used biological control methods such as larvivorous fish in potable water[34] and in non-potable water[25], and Bti[27,30,34]. Two studies used mechanical interventions[28, 29]. Additional chemical insecticides, including methoprene-S, permethrin, cypermethrin and clorpyriphos, were used in five of the studies[25,30,31,36,39].

All combination intervention studies except for two[24, 25]used temephos at a dose of 1ppm. All studies used temephos sand granules except for two studies [24, 35],which used temephos as emulsifiable concentrate. Only in study [30] temephos had been provided routinely before the intervention. In study [38],temephos was supplied for a nominal fee to households. In study [36],temephos was partially substituted with methoprene and in study[34],temephos was replaced with Bti because of its unpleasant odour. In study[27], the focal treatment with temephos was interrupted due to a dengue outbreak and supplemented with ULV spraying.

Most studies [24,25,26,27,29,33,34,35,36,37,38,39]used different community members/groups either as a target group for education or for the delivery of the intervention. Study [39] formed a community working group exclusively for the implementation of the control activities in order to analyse the importance of community participation.

Community-effectiveness.

Of 16 studies, 10[24,25,26,28,29,32, 34,35,38,39] reported a significant reduction post-intervention of immature Aedes stages as compared to baseline findings and control groups. Three studies [30,31,33] failed to reduce Aedes populations. Study [27]reported an initial drop in larval indices, however this was not sustained. Although larval breeding was reduced in study [36], the BI remained greater than 100 throughout the year. Study [37] reported only moderate effects of temephos on entomological indices.

For example, the effect of temephos on larvae in study [27] lasted 6 weeks, with infestations in treated containers detected after 6 weeks of treatment, whereas study [28]showed an effect of 6 months, with an observed increase of adult mosquito population 6–7 weeks post-treatment. In study [32], the effect on larvae lasted 8 weeks, study [35] showed a variation between 2–8 weeks, and for study [38] the effect waned after 3 months.

Four studies stratified their analyses according to the individual effect of each intervention, showing that temephos was the most effective intervention alone [32] or in combination with source reduction [24, 30] and ULV spraying [27].

While 10studies generally reported positive community-effectiveness parameters of the interventions [24,25,26,28,29,34,35,37,38,39], six studies [27,30,31,32,33,36]reported shortcomings related to attaining effectiveness.

From those reporting positive results, however study [28], while reporting successful outcomes in the short term, concluded that long term success depended on political commitment and community participation. Study[29] showed that factors such as high water turnover and temephos resistance in local vector populations contributed to decreased community-effectiveness. Another limiting factor was the limited knowledge of people about the interventions [25, 38].

In the group of studies reporting shortcomings these included problems related to surveillance and coverage[27],inadequate source reduction and larvicidal application [30], low acceptability of larvicides [36] and lack of resources and manpower [31].Other challenges included the limited residuality of temephos [27] and overflowing of water in containers resulting in consequent dilution of the active ingredient[33].

One important challenge raised regarding the use of temephos in combination interventions described in both groups was the false sense of security that can arise, leading the population to believe that temephos application alone is sufficient to prevent dengue which resulted in foregoing activities such as source reduction and other environmental management [24,33].

Acceptability.

Acceptability of temephos was not assessed in all studies but was found to be low in three studies [34,36,37] due to unpleasant odour. For this reason, study [34] replaced temephos with Bti as an intervention, and in study[36],temephos was partially substituted with methoprene. Also, the application of temephos was found to be labour intensive in study[24].