PubMed Health⌕ Search

Biomedical subjects

M M Milby

Publications and source records attributed to M M Milby.

27 records · Page 2Linked to original sources
PubMed1986

The influence of constant versus fluctuating water temperatures on the preimaginal development of Culex tarsalis.

Culex tarsalis larvae derived from field-collected egg rafts were reared outdoors in a deep pond with constant water temperature or a shallow pond with fluctuating temperature. No significant differences were found between ponds in the proportion of larvae surviving to adults, female autogeny rates or wing lengths of adults. The average time from 1st instar to adult emergence ranged from 8 days at 31 degrees C to 16 days at 17 degrees C. Males developed faster than females, and both sexes always emerged faster from the shallow pond than from the deep one. However, the temperature-adjusted mean emergence times were equal, and normalized cumulative development curves, fitted to a Weibull function, were identical for the 2 ponds.

Animals↗
PubMed1985

Aerial adulticiding for the suppression of Culex tarsalis in Kern County, California, using low volume propoxur: 2. Impact on natural populations in foothill and valley habitats.

A low volume formulation of propoxur wettable powder suspended in larvicidal oil was evaluated on 4 occasions in Kern Co., California during 1983 using fixed and rotary wing aerial application systems. Culex tarsalis abundance was suppressed significantly by all sprays, although reduction below the virus maintenance threshold of 30 females per trap night was achieved only at one foothill site. Western equine encephalomyelitis virus minimum infection rates decreased significantly after serial applications on 2 occasions at a valley site. However, virus persisted in the spray zone at minimum infection rates of greater than 1 per 1000 Cx. tarsalis females tested and transmission of virus to sentinel chickens continued. The parity rates were reduced significantly at 2 semi-isolated foothill sites, but not at a valley site where elevated autogeny rates increased the reproductive age of the host-seeking population. Spraying during late afternoon by helicopter resulted in better control than early morning applications by fixed wing aircraft at a valley site.

Aircraft↗
PubMed1979

Correlation of Culex tarsalis population indices with the incidence of St. Louis encephalitis and western equine encephalomyelitis in California.

Mosquito population indices from California for the period 1953-1973 were analyzed to determine their association with activity of St. Louis encephalitis (SLE) and western equine encephalomyelitis (WEE) viruses. Culex tarsalis female populations, as measured by New Jersey light trap indices (LTI), correlated positively with the incidence rates of encephalitis in humans, and were a reliable means of forecasting the years of highest incidence. The critical level of C. tarsalis in urban areas below which no human cases of SLE and WEE were detected was an LTI of 0.1. Critical urban levels of C. tarsalis associated with significant human SLE or WEE incidence ranged between LTIs of 6.4 (for rural mosquito abatement districts [MADs] with large resident human populations). Peaks in annual incidence of SLE and WEE in humans occurred during years when seasonal average C. tarsalis female populations in urban areas reached a LTI of 21. Peaks in weekly incidence of SLE and WEE were associated, respectively, with weekly LTIs of 21 and 81 in urban traps. Isolation rates of SLE virus from mosquito pools and transmission of the virus to enzootic hosts were highest when urban LTIs were between 10 and 19.9 and between 5 and 9.9, respectively. The WEE viral isolations and enzootic transmission rates were highest when LTIs in urban areas were 1-4.9.

Animals↗
PubMed1978

Study of homologous and heterologous antibody response in California horses vaccinated with attenuated Venezuelan equine encephalomyelitis vaccine (strain TC-83).

Of 359 horses vaccinated with attenuated Venezuelan equine encephalomyelitis (VEE) vaccine (strain TC-83), 87% developed hemagglutination-inhibition (HI) antibodies to VEE virus within 1 month. Blood from a subsample of 101 of the 359 horses was obtained over a 1-year period. Within 1 month after vaccination, 84% of the 101 horses had developed VEE HI antibodies, 87% had developed VEE-neutralizing (Nt) antibodies, and 78% had developed VEE complement-fixing (CF) antibodies. One year after vaccination, 58% of the horses had VEE HI antibodies and 73% had VEE Nt antibodies. The percentage of horses with VEE CF antibody titers dropped to a low level (46%) within 6 months after vaccination, and most horses were seronegative for VEE CF antibodies 1 year after vaccination. The presence of antibodies to heterologous (western equine or eastern equine encephalomyelitis, or both) alphaviruses suppressed VEE antibody formation in horses vaccinated with TC-83 vaccine. However, the proportion of horses that developed VEE antibodies exceeded levels that generally were believed adequate to suppress a VEE epizootic in a population. There was an 88% correlation between the HI and Nt tests for VEE antibodies.

Animals↗
PubMed1976

Relation of mosquito density to bird: mammal feeding ratios of Culex tarsalis in stable traps.

Stable traps, each baited with a jackrabbit and either a chicken or a pheasant, collected more than 21,000 mosquitoes in the Sacramento Valley, California, in 1972 and 1973. The focus of interest was the feeding behavior of Culex tarsalis, a primary vector of encephalitis viruses. Generally, feeding success was less and feeding rates on the jackrabbit were greater when larger numbers of mosquitoes were collected, or when a bird was exposed that was less receptive to mosquito feeding. Greater feeding rates on the jackrabbit apparently resulted from decreased feeding on the avian host and from diversion of mosquitoes to the jackrabbit. Figures are given that show how changes in feeding rates on birds affect the probabilities that a mosquito that feeds twice would feel both times on a bird, or on a bird and then on a mammal. Relatively small collections of nine mosquito species other than C. tarsalis revealed distinct species differences in feeding behavior. Aedes malanimon showed a preference for jackrabbit, which is relevant to its role as a vector of western equine encephalitis and California encephalitis viruses.

Aedes↗