摘要:

Abstract.Simulium (Trichodagmia) guianenseis an important Amazonian vector of onchocerciasis. Examination of the polytene chromosome banding patterns of larvae from five sites in Brazil revealed the occurrence of four cytotypes, designated A, B, C and D. The chromosomal standard,Simulium guianense A, occurred at two localities in Goias State (on the Rio Tocantins and Rio Mucambao) where it was the only cytotype. The other three sites examined yielded one different cytotype from each: B from Rio Oyapoque in Amapa State, C from Rio Tocantins in Maranhao State, and D from Rio Xingu in Para State. All cytotypes differed by at least two fixed inversions, but a sex determining system was not evident in any cytotype. As the cytotypes have been found allopatrically it is not certain that they represent sibling species; sampling of sympatric populations would resolve this. During certain times of the year, voracious anthropophagy byS.guianense sensu latooccurs at the localities sampled for cytotypes A, C and D (biting data are not available for the cytotype B locality). In some other areas, however,S.guianense s.l.is entirely zoophilic. Further studies are needed, therefore, to elucidate the biting habits, vectorial capacity, geographic distribution and taxonomic status of these four, and perhaps additional, cytotypes comprising theS.guianensecomplex.

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00716.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.A group of thirty‐two Merino sheep infested with itch mites(Psorergates ovis)and fed a maintenance diet which imposed moderate nutritional stress had a significantly higher mite population, significantly more skin scurf, and significantly more fleece damage or derangement (P10 per 200 cm2of skin area) in both groups, had more dermal mast cells than sheep with fewer mites irrespective of the plane of nutrition. Skin thickness and greasy fleece weight in die group maintained on the low plane of nutrition were significantly less(P<0.05) than in die well‐nourished group, reflecting the difference in protein and energy content of the two diets. Within the nutritionally stressed group, the sheep with low mite counts had a significantly lower(P<0.05) greasy fleece weight and a shorter mean staple length than the sheep with high mite counts. There was no significant difference in greasy fleece weight between sheep with low or high mite counts in the group fed on the high plane of nutr

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00717.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Statistically significant differences were observed in the population density of the horn fly,Haematobia irritans irritansL., on Angus cows having significantly different frame sizes. Angus cows, averaging126 cm in height at the hip. The Angus I cows(126 cm). The estimated heritability(h2)of horn fly resistance was 0.43 ± 0.07 and 0.95 ± 0.31 for 1989 and 1990, respectively. Horn fly counts on the Angus I herd (<112.5 cm in height) was 118.1 (probable breeding value, PBV = ‐20.69) to 165 horn flies per cow (PBV = 26.9 flies per cow in 1989) and from 75.9 (PBV = ‐29.1) to 134.5 (PBV = 29.5) flies per cow in 1990. Angus I bulls had PBV = ‐23.7 to 13.4 and from‐26.5 to 14.75 in 1989 and 1990, respectively. The Angus II cows had horn fly counts that ranged from 159.6 (PBV of‐23.5) to 208.1 (PBV of 25) per cow in 1989 and from 232.3 (PBV of‐56.2) to 378.7 (PBV of 90) per cow in 1990. Angus II bulls had PBVs that ranged from‐17.1 to 18.9 in 1989 and from ‐28.1 to 48.8 in 1990. The Angus I cows had significantly(P<0.0001) lower numbers of hom flies (mean of 63.8 horn flies per m2) than the small, medium or large Angus II cows (mean of 129.4, 149.6 and 145.5 hom flies per m2, respectively). The data indicated that some specific factor(s) associated with cow size contribute(s) to innate resistance

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00718.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.A vehicle‐mounted net was used to make hourly catches of blackflies at 700–1000 m altitude in the River Assob valley, central Nigeria, on 20 days during the dry season. Pearson Correlation Matrix analysis of the collection data and meteorology showed that the main factors affecting flight activity of each of the four most abundant blackfly species were primarily light intensity and secondly wind velocity, whereas relative humidity was the least important factor. Right activity showed a negative linear regression against wind, with some activity occurring in wind speeds up to 15 km/h. Distance‐weighted least‐squares (DWLS) regressions showed little correlation of temperature with activity forSimulium hargreavesiandS.adersi, butS.squamosumandS.voraxhad small peaks at 28d̀C and 31d̀C, respectively. DWLS regression against light intensity showed an activity peak at 6000 lux, except inSimuli

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00719.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.A field trial compared DDT house‐spraying with permethrin‐impregnated bednets for malaria control in Solomon Islands from 1987 to 1991. Mortality‐rates of malaria vectorAnopheles farautiin exit window traps were 11.6% from an untreated hut, 10.1% from a hut sprayed with DDT 2 g/m2, and 98% of those from a hut in which the occupants used bednets treated with permethrin 0.5 g/m2. Since bioassays of the DDT‐sprayed walls (15 min exposure in W.H.O. standard test cones) gave 77% mortality ofAnfarauti, it was concluded that the insignificant impact of DDT could be explained by the exophilic behaviour of endophagic vectors, whereas the greater impact of permethrin was attributed to the more effective exposure ofAnfarautifemales to the impregnated bednets ‐ attracted by the occupants. The parous rate was higher indoors, except in the area with permethrin‐impregnated bednets. It was therefore concluded that permethrin‐impregnated bednets reduced the mean longevity ofAnfarautiand hence its vectorial capacity. The circumsporozoite (CS) antigen positivity rateof Anfarautiin the DDT area was 0.18% outdoors, significantly less than 1.42% indoors. In the comparison area CS rates were 0.65% outdoors and 0.75% indoors. CS antigen was not detected inAnfarautifrom the bednet area, indicating the apparent prevention of malaria transmission. As DDT spraying was so much less effective, it was discontinued in 1993 and permethrin‐impregnated bednets are now the principal malaria control method in

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00720.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.A self‐medicating applicator for killing ticks on deer and domestic ungulates by passive transfer of acaricides during feeding is described. The applicator consists of a barrel divided into a food bin (above) and a sealed self‐contained acaricide reservoir (below) with a vertical, centrally‐located ceramic column that extends from the reservoir into the food bin. Acaricide is drawn up the column from the sealed reservoir by absorption. Animals attracted to the food in the device acquire the acaricide during feeding when they contact the uppermost portion of the column.White‐tailed deer(Odocoileus virginianus)readily utilize the applicator in penned and natural conditions. In a field study, examination of hunter‐killed deer demonstrated that animals from a treated site were infested with many fewerIxodes scapularis(3.4 ± 1.1) than those from a control site (10.8 ± 3.0). Chromatographic analysis of hair samples revealed traces of permethrin on three of the four animals examined, suggesting use of applicators by these deer. In a study using penned goats{Capra hircus)infested withAmblyomma americanumticks, treatment efficacy reached 86.4% within 4 days of exposure to the applicators. Visual observations confirmed that all animals used the applicators. Gas chromatographic analysis of goat hair samples indicated that permethrin was detectable on all of the treated animals exposed to

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00721.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.A survey of the dengue vector mosquitoAedes aegyptiwas undertaken using runnel traps to detect immature stages (larvae and pupae) in flooded disused mine shafts and wells in Charters Towers, Queensland, Northern Australia. The town has a history of dengue fever since 1885 when goldminers were the first recorded victims. During the latest dengue epidemic in 1993, 2% of the population had laboratory‐confirmed dengue virus Type 2, despite source reduction ofAe.aegyptibreeding‐sites at ground level or above. This led to suspicions that dengue vectorAe.aegyptibreeding‐sites might be below ground level. When surveyed in March 1994,Ae.aegyptiimmatures were found in 9/10 wells and 1/6 mine shafts. The water in wells and mines had similar characteristics ‐except that turbidity was higher in the mines, which more often contained predators of mosquito immatures.The copepodMesocyclops aspericorniswas collected from water in 1/10 wells and 2/6 mine shafts. Laboratory predation trials resulted in 95.5–100% predation by 25 copepods/1 onAe.aegyptifirst‐instar larvae up to 200 larvae/1. Five wells containingAe.aegyptiin the survey were inoculated with fifty indigenousM.aspericornis, and five wells (one positive and four negative in the survey) were left untreated as controls. Nine months later, in December 1994,Ae.aegyptihad been eliminated from all five treated wells but all untreated control wells containedAe.aegypti, except for one well that contained a natural populationof M.aspericornis.The role of wells and mines as winter/ dry season refuges ofAe.aegyptiin northern Australia is reviewed, and we recommend the use ofM.aspericornisas a cost‐effective, environmentally acceptable and persistent agent for the sustainable control ofAe.aegypti, especially in inaccessible b

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00722.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) analysis was used to characterize mitochondrial DNA (mtDNA) variation in screw‐worms,Cochliomyia hominivorax, and secondary screwworm,C.macellaria, from the Caribbean, North America and South America. Four amplicons, totaling 7.1 kb, were analysed with sixteen restriction enzymes. A total of 133 restriction sites was observed in the two species, 104 inC.hominivorax, of which nineteen were variable, and ninety‐five inC.macellaria, none of which was variable. Fourteen mtDNA haplotypes were observed among eighteenC.hominivoraxexamined. Mean divergence betweenC.hominivoraxhaplotypes(d)was 0.0064 substitutions per base‐pair and genotypic diversity(G)was 0.97. Mean divergence betweenC.hominivoraxandC.macellariawas 0.0824.Cochliomyia hominivoraxhaplotypes could be divided into three assemblages representing North America, South America and Jamaica, based on UPGMA clustering withdvalues. The assemblages did not exhibit complete geographic fidelity. These data were discordant with previously published allozyme data indicating little differentiation between screwworm populations. A scenario invoking historically isolated populations coming into contact with the introduction and movement of European livestock is proposed to explain the observed population structure of

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00723.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The relationship between female mosquito body size and survival rate was studied in field populations ofAnopheles arabiensisin the Awash valley, central Ethiopia. Body size was quantified by measuring the wing‐length. Highly significant correlations were found between size, parousness and insemination. It was concluded that largerAn.arabiensisfemales have a higher probability of survival, being inseminated and producing more egg batches than smaller adults. Implications for vectorial capacity and vector competence of mosquitoes are discusse

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00724.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.We investigated the identity and distribution of members of theCulicoides variipenniscomplex in the six New England states of the U.S.A., a region where bluetongue transmission has not been detected. Analyses of seven polymorphic isozyme‐encoding loci showed that onlyC.v.variipennis, not considered to be a vector of the bluetongue viruses, was present. The populations ofC.v.variipenniswere significantly more hetero‐zygous thanC.v.sonorensisandCv.occidentalispopulations from similar studies in the state of California. Estimates of genetic diversity among populations ofC.v.variipennisin New England were similar toC.v.sonorensisin the state of Colorado, but were significantly more genetically divergent than California populations ofCv.occidentalis.The impact of these findings on the status of New England as a possible bluetongue‐free region for the purpose of international trade in ruminant livestock and their germplasm is disc

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00725.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY