Livestock Research for Rural Development 29 (3) 2017 Guide for preparation of papers LRRD Newsletter

Citation of this paper

The efficacy of ZeroFly® Screen, insecticide incorporated screen, against nuisance and biting flies on cattle kept under zero grazing system in the Northern Zone of Tanzania

Y P Nagagi, V Temba and E V G Komba1

Livestock and Human diseases vector control division, Tropical Pesticides Research Institute, PO Box 3024, Arusha, Tanzania
1 Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture, PO Box 3021, Morogoro, Tanzania


A field trial was conducted from December 2012 to June 2013 to assess the effectiveness of ZeroFly® Screen, an insecticide incorporated screen, against flies on cattle kept under zero grazing system in northern Tanzania. Six animals were distributed in as many standard zero-grazing enclosures. Two enclosures per site were constructed at three sites A, B and C. Animals housed in the enclosures at site A had their enclosures (A1, A 2) fitted with ZeroFly® Screen while those at site B (B1, B2) had insecticide free screen of the same material as ZeroFly® Screen. The remaining pair was kept in enclosures at site C (C1, C2) without any netting installed but were sprayed with Ectopor® SA 20 as per manufacturer’s recommendation to serve as the positive control. Baseline data on fly populations were collected prior to installation of Zerofly® Screens. Flies were then caught after every fortnight to monitor their populations. Biconical traps placed 3 - 5 meters away for a period of 48 hours, one for each enclosure were used to catch flies.

The results indicated that Zerofly® Screen when used alone is effective in controlling both biting and nuisance flies. The population density of tsetse flies at site A dropped from the mean catch of 3.75 flies/trap/day (FTD) before intervention to monthly mean catch of 1.75, 0.625, 0.5, 0.375, 0.25, 0, 0.25 FTD in December, January, February, March, April, May and June respectively. On the other hand, the population density of houseflies dropped from the mean catch of 103 FTD before intervention to monthly mean catch of 34, 11.25, 2.5, 2.75, 3.25, 2.5 and 3 FTD in December, January, February, March, April, May and June respectively. Tsetse fly population density was significantly (p=0.006) lower at site A when compared with site B. Nevertheless, there was no significant difference (p=0.872) between the population density of tsetse fly at site A and site C. The drop in population density of houseflies was significantly (p=0.000) lower with respect to site B. However, there was little to choose (p=0.922) between site A and site C. Laboratory findings showed that Musca domestica were highly susceptible than pregnant fed Glossina pallidipes. Although there was an increase in time for knockdown effect for the samples taken from mid December 2012 to mid June 2013, 100% mortalities were observed on all exposed flies. In this study, Zerofly® Screen has shown to be effective against tsetse flies and houseflies, hence can be used for control of nuisance and biting flies in Tanzania.

Key words: Glossina, houseflies


Livestock production is among the major agricultural sub-sectors in Tanzania (URT, Economic survey, 2010; Njombe et al 2011). It supports the livelihoods of about 37.0% of 4.9 million agricultural households (URT, Livestock sector development programme, 2011). In 2010, the sector grew at 3.4% and contributed about 3.8% to the Gross Domestic Product (GDP) of which 40.0% came from beef, 30.0% from dairy and the remaining 30.0% from other livestock commodities (URT, Economic Survey, 2010).

The dairy industry being an important component of the livestock sector has shown to be a source of animal protein, income and employment (Kurwijila 2001; Njombe et al 2011). It has a great potential to improve people’s livelihoods through improved nutrition arising from consumption of milk and income raised from sales of milk and milk products (Njombe et al 2011). Demand for dairy products in Tanzania is driven by a growing human population (currently estimated at 43 million and growing at 3.3% annually), urbanization (growing at 5.0% annually) and increasing incomes from high economic growth rate (real GDP growth currently about 4.0% per annum (MOAC/SUA/ILRI 1998). However, milk supply has failed to match with the growth in demand. Projections suggest that under current trends, production is very likely to fall short of demand (Swai et al 2014). These trends present an important income earning opportunity for current and potential smallholder dairy producers in Tanzania and their market agents, through dairy production, processing and marketing (Swai et al 2014).

Despite its importance in contributing to the economy and the well being of people in the country, the performance of dairy industry is not being exploited to its full potential (Njombe et al 2011). This is attributed to various constraints such as land, water and pastures, types of livestock and production systems, livestock diseases, livestock products processing and marketing, farmers’ knowledge and skills on livestock production as well as accessibility to credits (URT, National Livestock Policy 2006). Of the diseases, arthropod borne diseases are associated with poor performance of dairy cattle (Steelman 1976; Maia 2009). They have direct and indirect effects on animal production and rural development. They can directly affect animal production through causing annoyance and mechanically or cyclically transmitting diseases when infesting animals (Bauer et al 1999; Maia 2009). For instance, of the most commonly arthropod borne diseases is infectious bovine keratoconjuctivitis (IBK) (McConnel et al 2007). It is a highly contagious ocular bacterial disease transmitted by mechanical vectors, predominantly face fly (Musca autumnalis), the house fly (Musca domestica) and stable fly (Stomoxys calcitrans) (Brown et al 1998). In 2008, the dairy farm at Tengeru Livestock Training Institute (now Livestock Training Agency), Arusha region had a good number of dairy cattle which succumbed to the IBK (Emmanuel Sichwale 2012 personal communication). The eruption of the disease was observed to correlate with the period of high fly population in the area. Though the economic impact in monetary terms was not determined, decreased milk production and animal blindness were cited to be predominant outcomes. On the other hand, in Morogoro region at Kambala village it was shown that flies were associated with infectious bovine keratoconjuctivitis in cattle and trachoma in man (Mbilu et al 2007). Other arthropod parasites which attack livestock frequently are tsetse fly, horse fly and mosquitoes. The diseases frequently transmitted to livestock include nagana (African animal trypanosomiasis), dermatophilosis, lumpy skin disease, Rift valley fever and blue tongue.

The economic and public health impacts of flies are attributable to the fact that most of the African communities live in a very close relationship with their animals which are the main source of family income (Maia 2009). Often livestock are kept in stables directly outside households luring haematophagous insects in search of blood meals and secretions, thus increasing the number of livestock disease vectors in the homesteads (Bauer et al 1999; Maia 2009). In addition to disease transmission, arthropods cause nuisance which affect livestock production (Maia 2009). Nuisance leads to animal disturbance and reduction in feed-intake which significantly decreases their performance while diseases increase morbidity and mortality (Bauer et al 1999; Rowlands et al 1999; Kamuanga et al 2001; Maia 2009). Besides low production performance of cattle, the occurrences of diseases subject farmers to call for veterinary services and substantial investments in animal healthcare which further reduces farmers’ income. Thus, the income of the farmers is reduced and the animal performance potential is never attained. There is no doubt that the use of insecticides is an important component of control strategies against vector borne diseases of animals and man (Gratz and Jany 1994; Mbilu et al 2007). In order to put in place effective, environmental benign and economical control strategies, the use of ZeroFly® Livestock has been found to provide protection against biting and nuisance flies including tsetse flies in several Sub-Saharan African countries (Bauer et al 2006; Bingham et al 2013). Therefore, this paper presents the results on the evaluation of ZeroFly® Screen (Polyethylene screen incorporated deltamethrin at the rate of 3.0 – 4.0 g/Kg or 120-360 mg/m2) against nuisance and biting flies as well as tsetse flies on cattle kept under zero grazing system in Tanzania. The objectives to which the study was based include; (i) To assess the impact of ZeroFly® Screen on fly density on cattle kept under zero grazing; and (ii) To assess the bio-efficacy and persistence of deployed ZeroFly® Screen.

Materials and methods

Description of study area

The study was carried at Olmoti sub-village 25 kms North East of Sukuro Township. Sukuro village is located 102 kms north of Arusha town and North West of Simanjiro District Headquarters which is in the northern zone of Tanzania. The study area was selected based on the presence of tsetse flies (Glossina swynnertoni), stomoxynae, Tabanidae and muscinae (Davis, 2011). The vegetation includes short and medium perennial grasses, bushes and thicket typical of Serengeti rangelands (Cooke, 2007). Masaai pastoralists graze their livestock in the area especially during the drier seasons. The area is also a wildlife migration corridor (predominantly wildebeest, zebra, Thompson gazelle and hartebeest) being part of the migratory route from Tarangire National Park through Lolkisale Game conservancy.

Description of the test product(ZeroFly® Screen)

ZeroFly® Screen is branded product of 100% polyethylene which is one metre high incorporated with Deltamethrin at the rate of 4.0 Deltamethrin/ kg textile. The product has a UV protection incorporated to extend durability during outdoor usage. It is manufactured by Vestergaard Group S.A, a Company based in Lausanne, Switzerland. The product is used to provide long-lasting protection of livestock from nuisance and biting flies including tsetse flies.

The animals involved in the study

Six young cattle aged between eight to twelve months were obtained from a pastoralist with his informed consent. The animals were ear-tagged for ease of identification and dewormed using Albendazole 10% (Tramazole 10%, Univet Limited, Tullyvin Cavan, Ireland) in order to ensure proper handling and their well being during the trial period. They were also given Isometamedium chloride (Samorin®, Merial South Africa Pty (Ltd), veMidrand, South Africa) as prophylaxis against trypanosomiasis after being confirmed to be trypanosome free. The animals were zero grazed and had their health monitored to ensure their comfort and good health throughout the study.

Study design and data collection methods

The field trial of ZeroFly® Screen was carried out for six months, from December 2012 to June 2013. Three trial sites A, B and C located about 0.25 – 0.5kms apart were identified based on reconnaissance survey of the population densities of nuisance and biting flies including tsetse flies. Briefly, areas known to be infested with both nuisance and biting flies including tsetse flies were visited and sampling done using biconical traps baited using acetone and cow urine. Four to five biconical traps per square km were used (depending on the vegetation site) along transect at the interval not less than 200m apart. The biconical traps stayed for 48hrs but emptied after each 24hrs and catches identified and recorded. Deployment of biconical traps were also done after the information obtained from some of the Masaai pastoralists through village executive office (VEO). The sites geographical coordinates (A1 (4o 07.62S, 36o 40.24E), A2 (4o 07.58S, 36o 40.22E), B1 (4o 07.55S, 36 o 40.09E), B2 (4o 07.57S, 36o 40.08E, C1 (04o 07.77S, 36o 40.39E), C 2 (04o 07.77S, 36o 40.41E)). Site A and C were at approximately 40 to 60m from the Masaai bomas whose owners and cattle left two weeks before the trial started while site B was 250m away from site A (Figure 1). At each site two animal enclosures of comparable sizes (approximately 24 M2) were constructed using locally available materials such as woods and cut pieces of spiny shrubs. The distance between the respective enclosures was 40 – 80m. ZeroFly® Screen was attached to the enclosures A1 and A1. The untreated screen was mounted against enclosures B 1 and B2 in a manner described in the installation guide by the suppliers (Figure 2). Each of the six animals was assigned to its own enclosure where it would be kept each day for purposes of this study. Animals kept in enclosures C1 and C2 were treated with Ectopor® SA 020 (Cypermethrin high cis 80/20 trans 20g/L Norvatis, Kempton Park, South Africa) purchased from an agrochemical dealer in Arusha. Ectopor was applied once every four weeks according to the manufacturer’s recommendations on the product label. The pour on formulation was spread on the backline of the animal from the base of horns to the root of tail, and on either side of cattle in front of elbow joint and hind knee. Prior to the implementation of the trial, baseline data were collected on the fly population densities using bi-conical traps set for a period of 48 hours at each study site. The bi-conical traps were placed 3 - 5 m away, one for each enclosure. Three catches were made over a period of two weeks, each at three days interval.

After setting up the trial, data on fly catches were collected for 48 hours every two weeks, throughout the trial period and recorded as flies/trap/day (FTD). In order to evaluate the persistence of the insecticide over time clipped pieces of ZeroFly® Screen and of the untreated polyethylene screen were taken prior to deployment and then at the end of each month for 6 months. These were put in a plastic container, wrapped with aluminium foil and transported to Tropical Pesticide Research Institute laboratory where they were stored in a refrigerator at 4 oC. These were later used for bio-assay tests i.e. ability to cause mortality to Musca domestica and pregnant female fed Glossina pallidipes when exposed to them. The bio-assay tests were done in triplicate using 10 flies of different species but same generation per test material. The tests were done for both Musca domestica and pregnant female fed Glossina pallidipes. The 10 insects of each species were exposed to the clipped piece of ZeroFly® Screen and the same numbers exposed to the negative control (untreated netting material). The insects were exposed in the box covered by the test screen and subsequently released into another observation cage to prevent cross contamination, negative control was run first and control boxes were never used for the ZeroFly® Screen tests. In addition personal protection equipment (gloves and laboratory dust coats) were also changed when dealing with ZeroFly® Screen or controls.

Figure 1. Trial sites at Olmoti, Sukuro village in Simanjiro District

Figure 2. Site A; right enclosure A1 and left enclosure A2 (Olmoti, Sukuro village, 2013)
Data Analysis

Bi-monthly data collections on fly catches were consolidated to obtain monthly mean catches, i.e. flies/trap/day (FTD) for each particular species and normalized by log transformation. Species which did not occur consistently at all trial sites during establishment of the baseline data were not considered in the analysis; however, they were computed to obtain the average mean catches and tabulated to obtain the estimate percentage of species distribution in the study area. Therefore, houseflies and tsetse flies were used in the analysis as representative because they were normally distributed. The transformed monthly mean catch of the flies at intervened sites were statistically analyzed using one way ANOVA in the SPSS (version 16) to find if there was any difference. Excel program was used to illustrate the findings in graphs and histogram. The bio-assay data were expressed as percentage mortality and were corrected using Abbott’s formula (Schneider Orelli) as % mortality = {(% mortality in treatment - % mortality in control)/100 - % mortality in control} x 100 (Abbott 1925)


Population distribution of nuisance and biting flies

The population of flies for the two weeks survey at trial location was 88.46% of nuisance flies (Musca domestica (house flies), Fannia canicularis and Sarcophaga spp) and 11.54% of biting flies (Glossina swynnertoni (tsetse flies), Stomoxysis and Tabanus spp) in that order of prevalence. The percentage distribution of each species is shown in figure 3.

Figure 3. Population distribution of nuisance and biting flies at the trial site
Impact of ZeroFly® Screen on flies’ density

There was a marked decrease in fly population following installation of ZeroFly® Screen, at site A. The population density of tsetse flies dropped from the mean catch of 3.75 flies/trap/day (FTD) before intervention to monthly mean catch of 1.75, 0.625, 0.5, 0.375, 0.25, 0, 0.25 FTD in December, January, February, March, April, May and June, respectively. This was not the case at site B where the population density of tsetse flies (flies/trap/day) remained relatively higher than at site A and C throughout the trial period. The trend of tsetse fly population between the intervened sites is shown in figure 4. Tsetse fly population density was significantly (p=0.006) lower at site A when compared with site B. Nevertheless, there was no significant difference (p=0.872) between the population density of tsetse fly at site A and site C.

Figure 4. Population trend of tsetse fly at the intervened sites in Log [fly/trap/day]

Figure 5. Population trend of house flies at the intervened sites in Log [fly/trap/day]

On the other hand, the population density of houseflies dropped from the mean catch of 103 FTD before intervention to monthly mean catch of 34, 11.25, 2.5, 2.75, 3.25, 2.5 and 3 FTD in December, January, February, March, April, May and June respectively. Population density of houseflies at site B with untreated screen remained relatively higher that at site A and site C (Figure 5). The drop in population density of houseflies was significantly (p=0.000) lower when compared with site B. However, there was little to choose (p=0.922) between site A and site C.

Bio-efficacy and persistence of ZeroFly® Screen

ZeroFly® Screen insecticide incorporated screen remained intact during the whole period of the trial as the installed screen had no any noted torn portion. The bio-assay test of Zerofly® Screen on pregnant fed G. pallidipes showed 100% knockdown effect on samples taken from January to March within 5-15 minutes and 100% mortalities achieved at 3hrs to 6hrs while samples taken on April, May and June showed an increased time for knockdown effect between 20 – 150 minutes and 100% mortality achieved between 12 hrs – 24hrs. Similarly, houseflies were highly susceptible as the product had 100% knockdown effect to all samples taken from January to June within 1 – 10 minutes and mortalities achieved at 30 - 60 minutes.


The biting fly species found in this study were tsetse flies, Stomoxynae and Tabanus species while nuisance flies were houseflies,Fannia canicularis and Sarcophaga species. Glossina swynnertoni were the only tsetse species found at Olmoti, Sukuro village in Simanjiro district northern zone of Tanzania during the study period. Among the biting flies G. swynnertoni (15%) ranked first followed by Stomoxysis (11%) and Tabanus species (6%). G. swynnertoni is one of the most widely and abundant species of tsetse flies in the Northern zone of Tanzania (Malele et al 2011). This is the most important vector of Sleeping sickness in man and Nagana in livestock (Malele et al 2007). Stomoxysis and Tabanus species are also widely distributed and responsible for mechanical transmission of various livestock diseases including trypanosomiasis. On the other hand, houseflies, Sarcophaga species and Fannia canicularis are among the most commonly found insects in homestead of pastoral communities. They are responsible for causing nuisance and may transmit a number of diseases to man and his domesticated animals. Therefore, efforts towards control of biting and nuisance flies are of paramount importance for both public health and increased livestock productivity.

In this study, it has been found that Zerofly® Screen when used alone is effective in controlling both biting and nuisance flies. This is because biting flies are hematophagous flies that are attracted to odors of animals in the pens, they do not see the screen and land on it, and getting killed by the insecticide it contains (Torr 1998; William and Rogers 1976). Therefore, from the findings obtained, the mean catch of tsetse flies in January dropped to 0.625 FTD equivalents to 83.3% reduction in the second month after installation of Zerofly® Screen. However, the last four months recorded tsetse fly mean catch of 0.375 – 0 FTD which is equivalents to reduction of more than 90% when compared to the baseline measures. On the other hand, the mean catch of housefly in January was 11.25 FTD equivalents to 89.07% reduction. Nevertheless, mean catches of houseflies in the preceding months kept fluctuating but were in the range of 3.25 – 2.5 FTD which is equivalents to reduction of more than 96.8%. These results correspond to other studies done in some other countries of tropical Africa such as Ghana and Kenya by Bauer et al (2006; 2011). For instance, when evaluating the effectiveness of the product against tsetse flies Bauer and colleagues (2011) found a reduction of more than 90% within two months in the protected villages in Ghana and further reduction of more than 95% in the subsequent months. On the other hand, Maia (2010) found that protection of cattle using insecticide impregnated screen (impregnated with deltamethrin at the rate of 80 – 120 mg per square meter) brought a significant reduction of 70% of nuisance insects.

It is worth noting that in the current trial, there was no significant difference in monthly mean catches of both tsetse fly and houseflies between Zerofly® Screen and Ectopor® (one of the already proven products in the country in terms of controlling nuisance and biting flies); as revealed in the comparable monthly mean catches against tsetse flies (p=0.872) and houseflies (p=0.922). This could bring us to a suggestion that either of the products could effectively be used for the control of flies. However, Torr et al (2007) showed that interactive measures through combining the two control methods may prove to be more beneficial.

Laboratory bio-assay results showed that houseflies were more susceptible than pregnant fed Glossina pallidipes.. Although there was an increase in time for knockdown effect for the samples taken from mid December 2012 to mid June 2013, 100% mortalities were observed on all exposed flies. This implies that Zerofly® Screen can still remain effective even at the period of six month following installation in this agro-ecological zone which was characterised by hot and rain weather.



The authors would like to thank Vestergaard Frandsen Group SA, Lausanne, Switzerland for funding the study. Sincere appreciation should go to the Director General, and the Registrar of Pesticides, Tropical Pesticides Research Institute (TPRI) for allowing us to conduct this study. Thanks to Mr. Elias Kihumo and TPRI staff who participated in the field work and data collection. However, much credit to Joshua Odhiambo and colleagues of Vestergaard Frandsen Group SA, Nairobi, Kenya for their valuable advice in the study design and preparation of the manuscript. Last but not least, the pastoralist who availed his cattle for the trial.

Conflict of interest

The authors declare that they have no conflict of interest.


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Received 13 February 2016; Accepted 3 January 2017; Published 1 March 2017

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