Number Of Sand Flies Research Articles

An attempt to control Phlebotomine sand flies (Diptera: Psychodidae) by residual spraying with deltamethrin in a Colombian village.

An attempt was made to control phlebotomine sand flies biting indoors in a rural community near Cali, Colombia, using the residual insecticide "K-Othrine" (deltamethrin) sprayed on the inside walls of houses. Twelve houses were divided into matched pairs based on physical characteristics, one house in each pair being left untreated while the inside walls of the other were sprayed with 1% deltamethrin at a concentration of 500 mg a.i./m2. Sand flies were sampled each week using protected human bait and sticky trap collections for four months after spraying. The number of sand flies (Lutzomyia youngi) collected on sticky traps was significantly lower (P = 0.004) in the untreated houses than in the treated ones with which they were matched. This difference was not significant for L. columbiana; the other anthropophilic species were not present in large numbers. The numbers collected on human bait in treated and untreated houses were not significantly different for either species. Activity of the insecticide as determined by contact bioassays remained high throughout the study and failure to control the insects was attributed to two factors: the tendency of sand flies to bite before making contact with the insecticide and the fact that the number of sand flies that entered houses represented a relatively small proportion of the population in the wooded areas surrounding the settlement in the study.

Attraction of Lutzomyia longipalpis to human skin odours

Male and female Lutzomyia longipalpis sandfiles showed attraction to human skin emanations placed on warmed glass Petri dishes. Unfed virgin females were more strongly attracted than males, which also showed attraction. Four human subjects were tested and significant variation was found between the numbers of sandflies attracted to their skin emanations. This suggests that some individuals were more attractive than others. There was a significant difference between the response shown by sandflies from the Jacobina and Lapinha regions of Brazil, suggesting that sandflies from the Jacobina region were more anthropophilic. In addition, sandflies from Jacobina had a significantly higher level of activity than those from Lapinha. The role of sandfly attraction to humans as a risk factor in Leishmania transmission is considered.

Host feeding preference of Phlebotomus guggisbergi, a vector of Leishmania tropica in Kenya

Recently the sandfly Phlebotomus guggisbergi was found to be a vector of Leishmania tropica causing cutaneous leishmaniasis in the Laikipia focus, Kenya, but extensive searches have shed no light on the identity of the rural reservoir host(s). In order to discover more about the biology of the vector, a host feeding preference study was conducted on wild sandflies in their natural cave environment over a 6-month period. Solid state Army miniature (SSAM) traps, without light bulb, were suspended over cages with potential hosts or an empty cage control. The animals tested included sheep, goat, dog, cat, hamster, rabbit, giant rat (Cricetomys gambianus), crested rat (Lophiomys imhausi) and rock hyrax (Procavia capensis), all of which (except hamsters) are normally found in the vicinity of the study site. Sandfly collections from traps baited with goat, sheep, cat, dog, rabbit, or wild rodent species were significantly higher than the control, whereas trap collections with hamster and rock hyrax were not significantly different from the control. Numbers of sandflies collected from the goat, sheep and cat were significantly greater than from the rabbit and rodents. The sex ratio also varied between collections: larger animals attracted a higher proportion of female P. guggisbergi than did the smaller animals (P > 0.05). Therefore greater emphasis should be placed on surveying larger animals to assess their status as reservoir hosts for L. tropica in Kenya.

Use of Hollow Trees as Diurnal Resting Shelter by Lutzomyia shannoni (Diptera: Psychodidae) on Ossabaw Island, Georgia

Use of hollow trees as diurnal resting shelter by Lutzomyia shannoni Dyar was studied on Ossabaw Island, Chatham County, GA. This species was collected in large numbers from constrictive openings (tree holes) leading into living hardwood trees that contained larger internal hollows. Laurel oak ( Quercus laurifolia Michaux) and live oak ( Q. virginiana Miller) were the most commonly used species. Regression analysis demonstrated no significant correlation between mean number of sand flies trapped from individual tree holes and six environmental variables: tree species, crown class, and diameter of the trees containing the holes; and area, compass bearing, and height above ground of tree holes from which flies were collected. The mean number of sand flies captured from individual hollow trees in 1990 was similar to and significantly correlated with the mean number of sand flies collected from the same trees in 1988, indicating that the tree-hole niche is stable for sand flies over time at this site.

The use of permethrin-impregnated wall cloth (Mbu cloth) for control of vectors of malaria and leishmaniases in Kenya — II. Effect On phlebotomine sandfly populations

In order to evaluate the effect of permethrin-treated wall cloth against phlebotomine sandflies, a study lasting 26 months (February 1989 to March 1991) was conducted in Marigat Location of Baringo District, Kenya, an endemic focus of both visceral and cutaneous leishmaniases. In six experimental villages, a total of 2000 houses were fitted with cloth made of cotton and impregnated with permethrin EC 20% at a dosage of 0.5 g/m2 diluted in water. Houses in the two control villages were not fitted with cloths and were located 1.5 km away from the experimental area. Traps made of clear polythene sheeting were coated with castor oil and placed inside houses to collect endophilic sandflies. In the experimental villages, the permethrin-treated wall cloth (called Mbu cloth) reduced the population of sandflies found inside houses by 52-73%. Phlebotomus martini and P. duboscqi, vectors of visceral and cutaneous leishmaniases, were reduced by 76 and 85% respectively. In the experimental villages, highly significant differences were observed between the average numbers of sandflies collected before deployment of the treated wall cloth and those observed after the third treatment of the cloth. No major sandfly reduction was observed however, in the control villages. There was also evidence of feeding reduction due to the permethrin.

Effect of deltamethrin spraying on the sandfly populations in a focus of American cutaneous leismaniasis

The effect of deltamethrin of the sandfly population in a focus of American Cutaneous Leishmaniasis in Viana, Espírito Santo State is described. The phlebotomine population density was determined inside and outside houses during a one year period in a treated and untreated area. The results showed a significant reduction in the number of sandflies inside houses in the treated area compared with both the untreated area and the same area before spraying. Despite having a residual action for 12 months after spraying the insecticide was ineffective outside houses. It is concluded therefore that deltamethrin is an efficient insecticide for reducing the number of phlebotomine sandflies inside houses.

Leishmaniasis in Sardinia. III. Soil analysis of a breeding site of three species of sandflies.

Soil analysis was carried out on samples obtained from a breeding-site of the sandflies Phlebotomus perniciosus Newstead, P. perfiliewi perfiliewi Parrot and Sergentomyia minuta (Rondani) in Sardinia. Soil texture, pH, CaCo3, organic matter and water content showed no correlation with the number of sandflies that emerged from the places where soil samples were taken. It appears that pre-imaginal stages of these phlebotomine sandflies are associated with a relatively stable, cool and humid environment protected from sunshine and rain, rich in clay and in organic nitrogen.

Leishmaniasis in Brazil. VI. Observations on the seasonal variations of Lutzomyia flaviscutellata in different types of forest and its relationship to enzootic rodent leishmaniasis (Leishmania mexicana amazonensis).

Abstract The seasonal fluctuation of Lu. flaviscutellata is shown to be closely related to rainfall, the population of this species declining during the rainy season, between May and March, and increasing again during the dry season, reaching a peak towards December and January. A comparison of the numbers of Lu. flaviscutellata caught in different types of forest showed that this species is more common in the wetter forests of the “igapo” than in the drier “terra firme” forests, although similar seasonal fluctuations are noted in both types of forest. The close correlation between the numbers of Lu. flaviscutellata and the incidence of initial infections of Leishmania mexicana amazonensis in Oryzomys capito indicates that the major factor controlling the incidence of leishmaniasis is the number of sandflies.

Experimental infection of Panamanian Phlebotomus sandflies with Leishmania

Over 800 Phlebotomus sandflies of five species were fed artificially, by the Hertig pipette method, on a mixture of blood and flagellates from cultures of Leishmania braziliensis, s. lat. Flagellate infections of the gut were produced in all five species, with an over-all infection rate of 81%. As in the case of experimental sandfly infections with Old World species of Leishmania causing human disease, growth of the flagellates characteristically took place at the anterior station, i.e., in the cardia and at the proventricular valve, with occasional growth forward into the pharynx. In addition, however, there was usually attachment and growth in the hindgut, particularly in the thin-walled, slightly expanded anterior portion. Attempts to transmit the infection by feeding infected sandflies on spiny rats ( Proechimys) and a human volunteer were unsuccessful. The inoculation of suspensions of triturated sandflies into spiny rats, suckling white mice, and hamsters produced an infection only once, in a suckling mouse. A small number of sandflies of two species was fed with Leishmania enriettii. Infections of the cardia were produced in one species; the other was completely negative.

Addendum

Phlebotominae sand flies have been involved as vectors of Leishmania. In Argentina, Nyssomyia neivai and Nyssomyia whitmani are involved as the main vectors of American Tegumentary Leishmaniasis (ATL). In the northeastern border of the country, an outbreak of ATL during 2004–2005 was associated with deforestation and subsequent settlement of farmers close to the edge of the forest. The aim of this work was to study the community composition of sand flies along time in farms located near primary and secondary forest in two environments: houses and pigsties. The association of abundance with temperature and precipitation was also evaluated for the most prevalent species. A total of 23,659 Phlebotominae belonging to the genera Nyssomyia, Migonemyia, Pintomyia, Evandromyia, Micropygomyia, Sciopemyia, Dampfomyia, Psathyromyia and Brumptomyia were captured. Ny. whitmani, which was the most abundant species, and Migonemyia migonei, which was the second most abundant species, were present throughout the year. Both species were positively associated with temperature, mostly up to 31–47 days, and with precipitation at 31 days before the sampling day. The abundance was higher in pigsties than in houses, but the time pattern was positively associated between both environments. These results confirm that Ny. whitmani is the dominant species in the study area and its presence throughout the year indicates a potential long period of ATL transmission. The presence of Mg. migonei as the second species in abundance is relevant, because it has been described as a secondary vector of the parasites of ATL and a putative vector of the agent of American Visceral Leishmaniasis. We discuss the role of the pigsty as the environment that attract more sandflies, taking into account the number of sand flies captured there, the distance from the home, and the association of sand fly abundance with each of the two environments.

Phlebotomus and Residual DDT in Greece and Italy 1

Summary and Conclusions 1. An evaluation in terms of Phlebotomus control has been made of the extensive DDT-malaria campaign which has been in progress in Greece since 1946. Observations were made in Attica and Crete throughout the sandfly season of 1948. 2. In unsprayed places the sandfly population was normal in abundance and distribution of species when compared with the reports of previous investigators. Nearly 3000 sandflies were caught and identified. 3. Sprayed buildings were uniformly negative for Phlebotomus of any species. Night observations out-of-doors showed sandflies to be at a very low level within sprayed areas. The testimony of the people was solidly to the effect that sandflies had been annoyingly abundant but ceased to bother them indoors after the first treatment, and that there has been little or no annoyance outdoors at night. 4. The reduced sandfly abundance in the cities of Athens and Canea, Crete, which have not been sprayed in toto, may be due in part to the peripheral effect of the many treated buildings scattered through the urban areas, and in part to the use of household sprays—factors which have not been measured. 5. A modification of the oiled paper trap is described. 6. The present status of leishmaniasis in Canea is compared with that of previous years. a. A very marked decline of kala azar had occurred prior to the use of DDT, and was associated with the destruction of infected dogs and the general reduction of the dog population. With the return of dogs to normal, it is difficult to assess the effect of the present low sandfly level because of lack of information about factors such as other reservoirs and normal kala azar cycles. b. A sharp drop in oriental sore with the development of relatively few cases in the last two years, coincided with the introduction of DDT in 1946. c. Definite conclusions on leishmaniasis control must await long-term observations in endemic foci. 7. A recently initiated project for the control of oriental sore in the Abruzzi, Italy, was visited. Observations on the dominant sandfly and supposed vector, P. perfiliewi, were made in treated and untreated areas. There was witnessed the actual destruction of great numbers of sandflies on encountering residual DDT, resulting apparently in the progressive reduction of the local sandfly population. 8. In Sardinia, where every man-made structure has been treated with DDT, houses were negative eight or nine months later, and sandfly incidence was at an extremely low level. 9. On the basis of the present and previously published work, the following general conclusions seem warranted: a. Treatment of interiors with residual DDT gives immediate and virtually complete protection from sandflies indoors. b. House spraying alone, in compact communities, with an annual, preferably pre-season, treatment, eventually reduces the Phlebotomus population within the sprayed areas to near the vanishing point.

Phlebotomus (Dampfomyia) anthophorus, n. sp., and Phlebotomus diabolicus Hall from Texas (Diptera: Psychodidae)

During the summer of 1944 a large number of sandflies of the genus Phlebotomus was collected at Uvalde, Texas, and brought to Houston in an effort to establish a laboratory colony. Although sandflies had been collected in and around human habitations during the latter part of May and early June, none was found in such localities during July, August or the first part of September. Towards the end of September sandflies were again obtained from human habitations. During the months of July, August and September sandflies were collected from a rabbit pen attached to the Field Experiment Station of the U. S. Bureau of Entomology and Plant Quarantine. The specimens found in and around homes, biting human beings, were identified as Phlebotomus diabolicus Hall, 1936. Those collected from the rabbits proved to be a previously undescribed species possessing a number of unusual characteristics which warrant the erection of a new subgenus to include it, for which the name Dampfomyia is proposed. The specific name anthophorus is proposed for this new form, based on the peculiar characters of the spermatheca. A description of Phlebotomus (Dampfomyia) anthophorus, and an amended description of Phlebotomnus diabolicus are given below.

On the Relation ofPhlebotomus papatasiito the Temperature and Humidity of the Environment

The bionomics of sandflies (Phlebotomus: Psychodidae) have been studied mainly in relation to the diseases they transmit. Comparatively little experimental work has yet been undertaken on the physiology ofPhlebotomusin the laboratory. In the present paper experiments are described on the thermal limits ofPhlebotomus, on the influence of temperature and humidity on the length of life of adult sandflies and on the loss of water in larvae and pupae. The problem of loss of water in sandflies is of particular interest, since adjustment to a varying humidity under natural conditions appears to be an important factor in the transmission of diseases by these insects.For the study of sandflies in the laboratory an ample supply of insects raised under uniform conditions is required. In a previous publication (1934) a breeding method has been described which provides any desired number of sandflies. If overcrowding of the breeding pots is prevented the flies are relatively uniform.The species used in the experiments wasPhlebotomus papatasii, the common sandfly of the Mediterranean, which is the most suitable species for laboratory work; it is comparatively easy to breed and to handle and feeds readily in captivity. The sandflies used in the experiments were bred from females caught in October in Jerusalem. The pots containing the larvae were wrapped in moist cottonwool and survived the transport to London without any damage. The work was commenced, and parts of it completed, in the Department of Entomology, London School of Hygiene and Tropical Medicine, where I held the Avebury Studentship. It is a pleasure to acknowledge the help received from Professor P. A. Buxton and the valuable collaboration of Mr. J. D. Gillett. The work was completed in Jerusalem.