摘要:

Abstract.Various formulations of six insecticides (a carbamate and five pyrethroids), were impregnated into bednets and curtains made from cotton, polyester, polyethylene or polypropylene fabric. For bioassays of insecticidal efficacy, femaleAnopheles gambiaemosquitoes were made to walk on the fabrics for 3 min and mortality was scored after 24 h. The main concentrations tested were: bendiocarb 400 mg/m2, cyfluthrin 30–50 mg/m2, deltamethrin 15–25 mg/m2, etofenprox 200 mg/m2, lambda‐cyhalothrin 5–15 mg/m2and permethrin 200–500 mg/m2. Field trials in Tanzania used experimental huts (fitted with verandah traps) entered by wild free‐flyingAnopheles gambiae, An. funestusandCulex quinquefasciatusmosquitoes.Results of testing the impregnated fabrics in experimental huts showed better personal protection provided by bednets than by curtains. Permethrincis:transisomer ratios 25:75 and 40:60 were equally effective, and the permethrin rate of 200 mg/m2performed as well as 500 mg/m2. Bioassay data emphasized the prolonged insecticidal efficacy of lambda‐cyhalothrin deposits, except on polyethylene netting. Most of the impregnated nets (including the ‘Olyset’ net with permethrin incorporated during manufacture of the polyethylene fibre) and an untreated intact net performed well in preventing bothAnophelesandCulexmosquitoes from feeding on people using them overnight in the experimental huts.Anophelesshowed high mortality rates in response to pyrethroid‐treated nets, but only bendiocarb treated curtains killed manyCulex.Holed nets treated with either cyfluthrin (5 EW formulation applied at the rate of 50 mg a.i./m2) or lambda‐cyhalothrin (2.5 CS formulation at 10 mg a.i./m2) performed well after 15 months of domestic use. Treatment with deltamethrin SC or lambda‐cyhalothrin CS at the very low rate of 3 mg/m2gave good results, including after w

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Groups of cattle of four different cross‐breeds (Ankole × Friesian, Ankole × Brown‐Swiss, Ankole × Guernsey, Ankole × Sahiwal) plus a group of pure Ankole cattle were immunized against tick‐borne diseases: East Coast Fever, using aTheileria parvatrivalent vaccine, and anaplasmosis, babesiosis and, subsequently, heartwater. With the exception of two small subgroups of Ankole and Ankole × Sahiwal which were treated by weekly spraying using Delnav, all the groups were exposed to natural field challenge of ticks to quantify the development of host resistance to ticks. The results indicate resistance to the most abundant species,Rhipicephalus appendiculatus, as follows: Ankole>Ankole × Sahiwal>Ankole × Brown Swiss>Ankole × Friesian>Ankole × Guernsey. In bothAmblyomma variegatumandRhipicephalus evertsi evertsi, the manifestation of different levels of resistance between breeds is inapparent. Correlations between total ticks and standard female ticks were good forR. appendiculatus(r = 0.73) andR. evertsi (r ‐0.51) but poor forA. variegatum (r= 0.31). Correlations between species were reasonably consistent (r = 0.43‐0.59). There was no significant correlation between tick burdens and daily liveweight gain (DLWG) over the. whole period of the study. Of the cross‐bred groups, Ankole × Sahiwal, which had the highest level of resistance, had the highest DLWG. In contrast, the Ankole × Guernsey which developed the lowest level of resistance had only marginally lower DLWG, the difference being only 8 g/day. During the first period of exposure to ticks, however, the untreated Ankole × Sahiwal group had markedly lower DLWG, which may indicate that the development and manifestation of resistance is at the

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The basic reproduction number,R0, can be used to determine factors important in the ability of a disease to invade or persist. We show how this number can be derived or estimated for vector‐borne diseases with different complicating factors. African horse sickness is a viral disease transmitted mainly by the midgeCulicoides imicola.We use this as an example of such a vector‐transmitted disease where latent periods, seasonality in vector populations, and multiple host types may be important. The effect of vector population dynamics which are dependent on either host or vector density are also addressed. If density‐dependent constraints on vector population density are less severe,Rois more sensitive to vector mortality and the virus development rate. Host‐dependent vector dynamics change the relationship betweenR0and host population size. Seasonality can either increase or decrease the estimate ofR0, depending on the lag between the peak of the midge population and the infective host population. The relative abundance of two host types is a factor in the ability of a disease to invade, but the strength of this factor depends on the differences between the hosts in recovery from infection, mortality and transmission. Removal of a reservoir host may inc

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The mosquitoesAedes notoscriptusandCulex annulirostris, previously shown to be competent vectors ofDirofilaria immitis, were allowed to feed on dogs with densities of microfilariae ranging from 2665 to 33,055 microfilariae/ml. Filaria developed in both species at a similar rate independent of the initial microfilarial density.Cx annulirostrisingested more microfilariae although the number of developing larvae was consistently greater inAe. notoscriptus;one femaleAe. notoscriptuscarried sixty‐two third‐stage larvae 10 days after feeding, although no more than twelve were found inCx annulirostris.The mortality rate ofAe. notoscriptusin the first 3 days of filarial development was related to increasing microfilarial density, and was greater than that ofCx annulirostris, which quickly reduced its worm load and survived with fewer third‐stage larvae but for longer thanAe. notoscriptus.The vector efficiency index was higher at all microfilarial densities forAe. notoscriptus, but its survival was much reduced, and thereforeCx annulirostrismay be the more effective vector in localities where dogs have very high parasita

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.The human body louse,Pediculus humanus, showed eighteen midgut proteins ranging between 12 and 117 kDa, when analysed by SDS‐PAGE electrophoresis. Seven of them (12 kDa, 17 kDa, 29 kDa, 35 kDa, 40 kDa, 55 kDa and 97 kDa) were major bands based on their intensity of staining. The immunization of rabbits with a midgut extract elicited the production of protective polyclonal antibodies. These antibodies reacted strongly with all major midgut proteins as well as with 63 kDa and 117 kDa proteins when tested by the Western blot technique. The analysis of the proteins revealed that the 12 kDa, 25 kDa, 29 kDa, 35 kDa, 45 kDa, 87 kDa and 97 kDa proteins are glycosylated and none of them contained a lipid moiety. By electroelution, the proteins of 35 kDa and 63 kDa were purified. On trypsinization, the proteins of 35 kDa and 63 kDa produced four major fragments (F, F2, F3, and F4) when resolved on a 18% SDS‐PAGE. The Fj fragment of the 35 kDa protein reacted with me polyclonal antibodies by the immunoblot techni

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Karoo paralysis, caused by feedingIxodes rubicundusfemales, is a major disease of small stock in South Africa. Control methods currently practised are almost exclusively chemical based. To limit overdependance on chemicals, vegetation management was investigated as a possible method for control, to be incorporated in an integrated tick management system. Laboratory and field experiments were conducted to determine, firstly, the extent of vertical migration and survival of ticks on long and short copper rods which simulated grasses as questing substrates; secondly, the infestation burdens of sheep exposed to similar tick challenges in pens with long and short grass; and thirdly, the effect of trimming the lower crown line of wild olive trees, simulating the browsing effect of goats, on tick density in the immediate environment of the trees. When ticks were exposed to optimal (>45 cm) and sub‐optimal (<10 cm) length rods on which to quest, the extent of vertical migration over extended periods of time (up to 87 days) was significantly higher (P<0.001) for the ticks exposed to long rods. Also, almost 3 times as many ticks exposed to long rods survived compared to those exposed to short rods. Sheep exposed to long grass were infested by twice as many ticks compared to those exposed to short grass. Tick density at modified wild olive trees (Olea europaea africana) (0.027 ticks/m2) differed significantly (P<0.05) from that at control trees (0.088 ticks/m2). It is recommended that coarse grazers such as cattle and horses should be used to graze down long grasses before sheep are introduced into camps known to be infested withI. rubicundus.Similarly, domestic goats can, through their browsing effect on shrubs and trees, modify the vegetation and as such play an important role in an integrated tick management syste

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.From May 1984 to May 1985, the transmission of onchocerciasis by blackflies (Dipteria: Simuliidae) was studied around Gilgel Ghibe and Gojeb rivers in southwest Ethiopia. The predominant anthropophilic species ofSimuliumat both localities wereS.(Edwardsellum) damnosum sensu lawandS.(Lewisellum) ethiopiense.SomeS.(Anasolen) dentulosumalso landed on human bait at Gilgel Ghibe river.Dissections ofS. damnosumfrom Gilgel Ghibe and Gojeb revealed mean parous rates of 92% (n = 18,291) and 84%(n =9530), respectively.S. ethiopiensefrom Gilgel Ghibe and Gojeb showed mean parous rates of 53% (n = 322) and 93% (n = 14), respectively. Of the parousS. damnosum, 1.3% at Gilgel Ghibe and 0.5% at Gojeb harboured infective third‐stage larvae (L3) ofOnchocerca volvulus(or morphologically indistinguishable from it). Unknown filariae of animal origin, indicative of zoophily, were found in 0.3% and 0.7% ofSimulium damnosumcomplex females from Gilgel Ghibe and Gojeb, respectively.S. ethiopienseharboured developing (L,) larvae only, with 7.7% infection rate in both localities. In contrast,S. dentulosumdid not harbour any filaria larvae. The annual infective biting rate (AIBR) and transmission potential (ATP) of theS. damnosumcomplex at Gilgel Ghibe river were 858 and 5478, respectively. The AIBR and ATP ofS. damnosum s.I.at Gojeb river were 519.5 and 1963, respectively. These results emphasize the predominant role of theS. damnosumcomplex in the transmission ofO. volvulusin southwest Ethiop

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.During field studies (December 1988 to April 1990) to determine the vectors of visceral leishmaniasis (kala‐azar) in the Aba Roba (Segen Valley) focus of southern Ethiopia, a total of 40,770 sandflies (Diptera: Psychodidae: Phlebotominae) were collected and identified as six species ofPhlebotomusand seventeenSergentomyiaspp. Nine of these species were anthropophilic (fourPhlebotomusand fiveSergentomyiaspp.), the dominant beingPhlebotomus (Synphlebotomus) martini, P.(S.)celiae and Sergentomyia (Sergentomyia) schwetzi. P. celiaeadult populations increased during the rainy season. Of 2326P. martiniand 1044P. celiaedissected, the parous rate was 29.9% and 24.4%, respectively.Leishmaniapromastigotes were detected in sixteenP. martini(eleven identified asL. donovaniby isoenzyme analysis and/or a DNA probe) and in threeP. celiae(two identified by DNA probe), giving overall infection rates of 0.7% (1.9% parous infection rate) and 0.3% (1.2% parous infection rate), respectively. Four isolates fromP. martiniwere typed by their isoenzyme profile asL. donovanizymodeme MON‐37 = LON‐44, identical to one of the zymodemes isolated from patients in this focus. This is the first evidence thatP. celiaeis a vector and the first time thatP. martinihas been implicated in Ethiopia. Based on observations of abundance, seasonality and prevalence of infection of the twoSynphlebotomusspp., it is concluded thatP. martiniis the major vector andP. celiaea secondary vector in the Aba Roba focus. The risk of infection withL. donovaniis greatest during the wet s

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00082.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Restriction fragment length polymorphisms in polymerase chain reaction amplified fragments (PCR‐RFLP) of mitochondrial DNA were used to differentiate species of New World screwworms (Diptera: Calliphoridae). Twenty‐seven restriction enzymes were screened on five regions of mtDNA. Eleven restriction fragment length patterns differentiated New World screwworm,Cochliomyia hominivorax(Coquerel), from secondary screwworm,Cochliomyia macellaria(R). Five restriction fragment length patterns were polymorphic inC. hominivoraxwhile all fragment patterns were fixed inC. macellaria.Diagnostic restriction fragment length patterns were used for species diagnosis, whereas intraspecific variable patterns were used to characterize field samples and laboratory strains. The PCR‐RFLP technique is flexible with regard to developmental stage of the sample and method of preservation. We were able to characterize specimens of all life stages from egg to adult including larvae preserved in alcohol and pinned adults. PCR‐RFLP is rapid and inexpensive, enabling specimens to be characterized within 24 h for less th

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00083.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract.Previous use of permethrin‐impregnated bednets (mosquito nets) and curtains in four Kenyan villages for one year, 1990‐91, raised the permethrin LT50ofAnopheles gambiaeto 2.4‐fold above its baseline value, designated permethrin tolerance (PT), as measured by exposure to 0.25% permethrin‐impregnated papers in W.H.O. test‐kits. During 1992‐93, with ongoing use of permethrin‐impregnated nets and curtains, PT regressed slightly compared with the contemporary susceptibility level of An. gambiae from non‐intervention villages, to 1.8‐fold in 1992 and only 1.6‐fold in 1993. Thus the selection pressure of impregnated nets for PT inAngambiaeappears to be minimal in our study villages, although the impact of permethrin was demonstrated by a significantly lower parous‐rate ofAngambiaefemales in the intervention (63–66%) than in non‐intervention (79%) villages, and by reduced malaria transmission (reported elsewhere).In a selected stock ofAn. gambiaefrom the study area, PT did not affect the susceptibility to deltamethrin, fenitrothion, propoxur or DDT. Bioassays described herein provide easy procedures for field‐monitoring of mosquito susceptibility/tolerance/resistance to insecticides used for net impregnatio

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1996.tb00084.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY