Biomedical subjects
Publications and source records attributed to S M Presley.
A commercial inline constant flow valve for hand-compression hydraulic sprayers was tested to evaluate its capability to maintain constant pressure to the nozzle down to a preset cut-out pressure. The flow-control valve provided consistent flow rates when used with the H.D. Hudson X-Pert 9.5-liter hand-compression sprayers. This flow valve may have potential for use in vector control operations.
In 1993, Rift Valley fever (RVF) virus reappeared in Egypt. We determined the prevalence and feeding patterns of mosquitoes in 5 villages where the virus was active. Of 10 species recovered, Aedes caspius (Pallas), Culex pipiens L., Cx. antennatus (Becker), and Cx. perexiguus Theobald constituted 99% of > 35,000 mosquitoes captured in dry ice-baited CDC light traps. Ae. caspius was most prevalent, except at Nag' El Hagar where it was replaced by Cx. perexiguus. Cx. pipiens ranked 2nd, except at Nag' El Ghuneimiya, where it was replaced by Cx. antennatus. Most blood meals analyzed by an enzyme-linked immunosorbent assay reacted to > or = 1 antiserum. Cx. pipiens was mainly anthropophagic, and therefore may have been the main vector of RVF virus among humans. Ae. caspius feeds were chiefly from humans, bovines, and equines. Cx. antennatus and Cx. perexiguus fed generally on bovines. Mixed blood meals from humans and RVF virus susceptible animals were identified in the predominant mosquitoes. Prevalence and host selection, as well as predicted probability for a blood meal being interrupted, indicated that Ae. caspius may have served as a bridge vector between humans and bovines in 4 of the villages. Cx. perexiguus may have played this role at Nag' El Hagar. Because potential vectors are abundant, susceptible domestic animals are associated closely with humans, and surveillance of imported livestock is not systematic, we conclude that RVF virus sporadically will recur in Egypt.
Rabbit monospecific antibody Leishmania major surface glycoprotein (gp63) was used in an indirect immunofluorescence assay (IFA) to identify promastigotes and amastigotes from sandflies and lesion fluid aspirates, respectively. Anti-gp63 fluoresced the entire periphery and flagella of promastigotes of different Leishmania species at dilutions to 1:50. Promastigotes were distinctively demonstrated in whole infected sandfly homogenate for 17 days post-infection. Amastigotes from lesion aspirates of infected BALB/c mice and from a human cutaneous leishmaniasis case were also fluoresced by the antibody. This technique could prove to be especially useful in arthropod vector surveillance efforts in which detection of the pathogen is as important as speciation of the sand fly vector.
Twenty-four Hereford-Angus crossbred beef steers were exposed to 0, 75, 150, and 225 horn flies, Haematobia irritans (L.), per head under controlled environmental conditions. The physiological and nutritional indices of all steers were recorded during a 14-d infestation period. Overall rectal temperature increased in steers exposed to 225 H. irritans was per head. Feed intake and nitrogen consumption by steers exposed to 225 H. irritans was lower than uninfested steers during the first 4 d. Overall serum cortisol was lower in steers exposed to 150 or 225 H. irritans per head compared with unexposed steers. Compared with unexposed steers, packed cell volume (percentage) was lower in steers exposed to 150 H. irritans on days 4, 7, and 14, lower in steers exposed to 225 H. irritans on days 7 and 14, and lower in steers exposed to 75 H. irritans on day 14. Blood urea nitrogen (BUN) was higher on day 1 in steers exposed to 75 H. irritans per head compared with uninfested steers, whereas BUN was lower in 225 H. irritans-exposed steers on days 7, 10, and 14 when compared with uninfested steers. Our data, in conjunction with previously published data, suggest that rectal temperature increases in beef steers exposed to > 150 H. irritans per head, and water consumption and urine production increases at infestation levels > 225 H. irritans per per head. Our data were unable to resolve H. irritans effects on steer heart rate, respiration rate, urinary nitrogen excreted, nitrogen retained, and serum cortisol levels.
Reintroduction of Rift Valley fever (RVF) into Egypt in 1993 raised concerns about the potential for Egyptian mosquitoes to transmit the virus. We evaluated the ability of Aedes caspius, Culex pipiens, Cx. antennatus, Cx. perexiguus, Cx. poicilipes, and Anopheles pharoensis collected in the Aswan area and Cx. pipiens collected in the Nile Delta to transmit RVF virus. All mosquito species tested were susceptible to RVF virus infection, with An. pharoensis and Ae. caspius being the most sensitive to infection. However, none of 12 An. pharoensis, including 10 with a disseminated infection, transmitted RVF virus by bite. In contrast, nearly all Cx. pipiens (87%, n = 15) and Cx. perexiguus (90%, n = 10) with a disseminated infection transmitted virus. Overall transmission rates for mosquitoes exposed to hamsters with a viremia > or = 10(7) plaque-forming units/ml were Ae. caspius, 20% (n = 5); Cx. pipiens, 7% (n = 102); Cx. antennatus, 7% (n = 30); Cx. perexiguus, 11% (n = 9); and An. pharoensis, 0% (n = 7). Based on abundance, susceptibility to infection, ability to transmit virus, and feeding behavior, Ae. caspius appeared to be the most efficient vector of the Egyptian mosquitoes evaluated. While less susceptible than Ae. caspius, Cx. pipiens, Cx. antennatus, and Cx. perexiguus were also potential vectors during this RVF outbreak in Egypt.
The ability of colony-reared Phlebotomus bergeroti Parrot to successfully acquire and transmit Leishmania major (strain IPAP/EG 89/SI-177) was demonstrated in the laboratory. Female P. bergeroti were fed naturally on infected mice and artificially on infected blood suspension using a chick-skin membrane apparatus. Groups of sand flies, either infected on mice or by membrane feeding, were dissected and examined using light microscopy at 2-6, 8, 10, and 11 days postfeeding. Heavy promastigote infection of the thoracic and abdominal midgut was observed in 10% (2 of 20) of the naturally infected flies. Promastigote maturation was observed in 87% (81 of 93) of the artificially infected sand flies, with promastigotes observed in the cibarium and mouthparts at five days postinfection, and infective metacyclic stage promastigotes observed at eight days postinfection. Ten days postinfection, 31% (10 of 32) of the remaining artificially infected sand flies refed on an uninfected BALB/c mouse. Twenty-eight days following exposure to the infective sand flies, leishmanial lesions were observed on the pads of the mouse's front feet. The development of lesions on mouse foot pads clearly suggests the potential of P. bergeroti to serve as a vector for L. major.
Twelve adult female Anopheles sergentii were collected from 2 villages in the Nile River Valley in Aswan Governorate, Egypt, in August of 1993. No immature forms were found during limited sampling. This is the first record of this malaria vector in Aswan Governorate and represents the southernmost distribution in northern Africa.
Collections of Amblyomma americanum (L.) from five habitat types showed that significantly more ticks of all life stages could be collected by CO2-baited sticky traps than by the standard flagging technique. The effect of habitat type and season significantly influenced the number of ticks collected by both techniques. Traps baited with carbon dioxide revealed adult tick activity in several habitats several weeks earlier than did flagging, because flagging failed to efficiently recover ticks unless they had ascended vegetation. The CO2-baited traps required less time and effort and showed less variation for tick population surveys when compared with flagging.
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One hundred fifty Amblyomma americanum were examined between March and September 1986 from Cookson Hills Wildlife Refuge in eastern Oklahoma (USA). Of these ticks, 11% (17 of 150) were infected with Theileria cervi. Field-collected nymphal ticks had an 8% (3 of 37) prevalence of infection averaging 1.0 infected acini/nymph. Female ticks had a 16% prevalence of infection averaging 1.6 infected acini/female; T. cervi was not observed in salivary glands of field-collected male ticks. When laboratory reared A. americanum nymphs were allowed to feed on experimental white-tailed deer (Odocoileus virginianus) with varying T. cervi parasitemias (less than 1, 2, 6 and greater than 20%), only ticks which fed on deer with parasitemias greater than 1% became infected. Although prevalence and intensity of infection varied in the infected ticks, there was no significant difference in prevalence of infection between males and females. However, females did acquire significantly greater intensities than males. The data from these studies confirm that T. cervi overwinters in A. americanum and suggests that the prevalence, intensity and abundance of infection of T. cervi in ticks is influenced by the parasitemia of the deer host. Furthermore, fawns may play a more important role in the epidemiology of T. cervi transmission than do adult deer because of the coordination between tick activity patterns and deer fawning.