Interactive effects of turkeypox virus and Plasmodium hermani on Turkey poults.

Two experiments were conducted to examine the interactive effects of two disease agents of wild turkeys (Meleagris gallopavo), turkeypox virus and the malarial organism, Plasmodium hermani, on the health of turkey poults. Groups of domestic broad-breasted white turkey poults of 1 and 10 wk of age were infected with either turkeypox virus, P. hermani, both turkeypox virus and P. hermani, or were maintained as uninfected controls. The strains of turkeypox virus and P. hermani had been isolated from wild turkeys in southern Florida (USA). The goals of these experiments were two-fold and included both an examination of age differences in response to infections, and an examination of the effects of dual versus singular infections with the two agents. Both singular and concomitant infections of turkeypox virus and P. hermani were more detrimental to poults infected at 1 wk of age than to those infected at 10 wk, based on mortality, weight gain, and parasitemia. Dual infections of turkeypox virus and P. hermani were found to be slightly more harmful to 1-wk-old poults than were singular infections. No such interactive effects were noted in the poults infected at 10 wk of age.

Epizootiology of Plasmodium hermani in Florida: chronicity of experimental infections in domestic turkeys and northern bobwhites.

A pen-reared northern bobwhite and a domestic turkey were infected with a strain of Plasmodium hermani obtained originally from a wild turkey in southern Florida. Blood films from these 2 birds were positive microscopically for 188 and 370 days postinfection (PI), respectively. Culicine mosquitoes (Culex nigripalpus and C. salinarius) were blood fed on the bobwhite and the turkey at different times during the infection and used to transmit the malaria to other bobwhites and turkeys up to days 298 and 473 PI, respectively. It was concluded that in nature, P. hermani could remain in a chronic phase in avian hosts for a year, or longer, allowing survival of the parasite between seasons of mosquito transmission.

Temporal and geographic genetic variation in Culex pipiens quinquefasciatus (Diptera: Culicidae) from Florida.

Culex (Culex) pipiens quinquefasciatus Say field population from Vero Beach, FL, sampled monthly over a period of 8 mo, a colony sample, and six geographic samples were analyzed for genetic variation at 12 enzymes (10 "neutral" gene enzymes with 11 putative loci and two "complex" gene enzymes) by using polyacrylamide gel electrophoresis. The analysis of the 11 putative loci in both temporal and geographic samples showed that the four loci (Gpi, Hk, Mdhp-2, and Pgm) diagnostic of Cx. p. quinquefasciatus in the southern United States are present in similar frequencies in Florida samples. The Cx. p. quinquefasciatus colony sample showed significantly lower genetic variation than the temporal field samples, measured by mean number of alleles per locus (colony 1.2 +/- 0.1 versus field 1.44 +/- 0.03), percentage of polymorphic loci (colony 18.2% versus field 28.4%), mean observed heterozygosity (H(o) = colony 0.027 +/- 0.02 versus field 0.09 +/- 0.01), and mean Hardy-Weinberg expected heterozygosity (H(e) = colony 0.025 +/- 0.02 versus field 0.085 +/- 0.01). Three of the 11 loci (Acoh, Pgd, and Pgm) from the Vero Beach field samples showed bimodal patterns in their frequencies of the most common allele during peak density of the population. The low value of F(st) of 0.058 indicated minimum population substructuring among the temporal samples. Genetic variability values between geographic samples from the Florida panhandle and south Florida were not significant. Gene flow estimates based on F(ST), = 0.05, indicating low levels of gene flow among the geographic samples of Cx. p. quinquefasciatus. The average Nei's and modified Rogers' genetic distances among the six populations were 0.005 +/- 0.001 and 0.077 +/- 0.007, respectively. The cluster analysis did not suggest geographic clustering. The analysis of the "complex" gene enzymes in both temporal and geographic samples of Cx. p. quinquefasciatus from Florida showed the presence of two highly amplified esterases (Estbeta1 and Estalpha2\Estbeta2), indicating resistance to organophosphate insecticides and highly amplified Aldox enzyme (an enzyme that indicates resistance to at least one insecticide and a herbicide). Comparison of our results with previous studies on Cx. p. quinquefasciatus populations in the United States indicates that the genetic characteristics of the Florida populations of Cx. p. quinquefasciatus are very similar to populations from areas where ecological conditions are very different.

A review of monomolecular surface films as larvicides and pupicides of mosquitoes.

Commercially available monomolecular surface films (Arosurf MSF and Agnique MMF, non-ionic products) are utilized as larvicides and pupicides of mosquitoes. They are biodegradable and spread spontaneously over the surface of the water to form an ultra-thin film (monomolecular layer), about one molecule in thickness. Their mode of action against mosquito larvae and pupae is physical rather than chemical. They lower the water surface tension, preventing suspension of the larvae and pupae at the water surface, subsequently suffocating them. They also interfere with emergence of the adults. Monomolecular surface film products have been shown to be relatively safe to non-target invertebrates and vertebrates, including humans. The laboratory and field efficacy of monomolecular films against aquatic organisms, primarily mosquitoes, is reviewed and non-target effects reported.

Temporal and geographic genetic variation in Culex nigripalpus theobald (Culicidae: Diptera), a vector of St. Louis encephalitis virus, from Florida.

A field population of Culex (Culex) nigripalpus Theobald from Vero Beach, FL sampled monthly over a period of 24 mo, a colony sample and 10 geographic samples were analyzed for genetic variation at 14 enzyme loci using polyacrylamide gel electrophoresis. The Cx. nigripalpus colony sample showed significantly lower genetic variation than the field-collected samples, measured by mean number of alleles per locus (colony 1.4 +/- 0.1 versus field 2.1 +/- 0.22), percentage of polymorphic loci (colony 35.7% versus field 54.8 +/- 7.7%), but mean observed heterozygosity (Ho = colony 0.16 +/- 0.07 versus field 0.17 +/- 0.03) and mean Hardy-Weinberg expected heterozygosity (He = colony 0.14 +/- 0.06 versus field 0.18 +/- 0.02) did not differ significantly. Three of the 14 loci (Aldox, Gpd, and Gpi) from the Vero Beach field samples showed distinct temporal patterns in the frequency of the most common allele. Higher mean observed heterozygosity (Ho) occurred during months following high rainfall in the Vero Beach field samples than during months following low rainfall. The average Nm value of 3.6 indicated high gene flow among the temporally distributed samples of the Vero Beach population. Genetic variability values between geographic samples from Panhandle, FL and south Florida were not significant. Gene flow estimates based on F(ST) = 0.039 provided a Nm of 6.2 indicating high levels of gene flow among the geographic samples of Cx. nigripalpus. The average Nei's and modified Rogers' genetic distances among the 10 populations were 0.009 +/- 0.001 and 0.081 +/- 0.004, respectively. The cluster analysis did not suggest geographic clustering, Because Cx. nigripalpus is the vector of St. Louis encephalitis (SLE) in Florida, temporal and geographic genetic variation in this species is discussed in relation to the seasonal and geographic SLE virus activity in Florida.

Effectiveness and residual activity comparison of granular formulations of insect growth regulators pyriproxyfen and s-methoprene against Florida mosquitoes in laboratory and outdoor conditions.

Effectiveness and residual activity tests of granular formulations of 2 insect growth regulators (IGRs), s-methoprene and pyriproxyfen, against laboratory-reared larvae of 5 colonized mosquitoes, Aedes aegypti, Aedes albopictus, Aedes taeniorhynchus, Anopheles quadrimaculatus, and Culex nigripalpus, were conducted in the laboratory and outdoors in plastic tubs. Culex quinquefasciatus was exposed to these two IGRs in the laboratory only. Each IGR formulation was applied at 0.02 and 0.05 ppm active ingredient (Al) against 5 of the 6 mosquito species both in the laboratory and the outdoor evaluations, whereas Cx. quinquefasciatus was exposed to 0.2 and 0.4 ppm AI of s-methoprene, and 0.1 and 0.2 ppm AI of pyriproxyfen in the laboratory. s-Methoprene at 0.02 and 0.05 ppm AI resulted in variable levels (<39-100%) of inhibition of adult emergence in the 5 species monitored for 6 weeks after treatment under both test conditions. Aedes taeniorhynchus was the most susceptible to s-methoprene in terms of initial and residual activity. Culex quinquefasciatus and Ae. albopictus were the most tolerant to s-methopene, with maximum emergence inhibitions amounting to 84% in Cx. quinquefasciatus at 0.4 ppm and 44.3% in Ae. albopictus at 0.05 ppm during the 1st week in the laboratory. Pyriproxyfen at comparable treatment rates to s-methoprene caused very high levels (>80-100% in most cases) of initial and residual emergence inhibitions of the tested species in the laboratory as well as outdoors. In several species, pyriproxyfen induced complete inhibition of adult emergence for several weeks after treatment, even at the lower rate of 0.02 ppm. The World Health Organization has recently recommended the use of pyriproxyfen for the control of some mosquito species at specified rates in certain habitats.

Introducción, colonización, significancia médica y posibilidades de control de Aedes Albopictus en Estados Unidos de Norteamérica / Introduction, colonization, medical significance and control possibilities of Aedes Albopictus in the USA

Las poblaciones de Aedes albopictus fueron inicialmente descubiertos ya establecidos en el Estado de Texas en Estados Unidos de Norteamérica en 1985. Actualmente, Ae albopictus se ha diseminado a por lo menos 25 estados del área sureste atlántica media y algunos del área del medio oeste de Estados Unidos. La introducción de este artrópodo en ese país parece que ocurrió a través de la importación de llantas usadas procedentes de Asia del Norte. La diseminación rápida de Aedes albopictus en Estados Unidos ha llamado poderosamente la atención por la slud humana, porque se conoce que es posible vector de varios arbovirus de importancia en Salud Pública. En los estados de Missouri, Florida, Texas, Carolina del Norte e Illinois se han aislado 4 arbovirus de muestras colectadas de este artrópodo. Entre las medidas de control, se encuentran como notas más importantes la reducción de las fuentes de crecimiento, educación del público y conocimiento de la biología y ecología de este mosquito. Sin embargo, se han encontrado agentes biológicos de control como el grupo de mosquitos predadores Toxorhynchites, especies de copepodos y del Bacillus thurigiensis, serovar israelensis (B.t.i..), que han sido probados y/o usados en el campo para reducir las poblaciones de larvas de Ae albopictus. El uso de repelentes y otras medidas de protección contra la picadura de Aedes albopictus han sido investigadas. Los estudios de laboratorio empleando organo fosfatos (Ops), tiroides, pesticidas microbianos Bacillus hurigiensis, serovar israelensis y bacillus sphaericus y reguladores del crecimiento (IGRs) contra las larvas de una población de Aedes albopictus de Florida, indican que el grado de toxicidad va así: IGRs> piretroides> OPs>microbios. En pocos laboratorios y/o estudios de campo, adulticidas y larvicidas selectivos (inlcuyendo fórmulas de emisión lenta) han mostrado bajo potencial para el control de este mosquito. Los adulticidas como malathion, permethrión, resmecthrin sinergístico (Scourge) y otros usados en varias situaciones en el área atlántica media y sud este de Estados Unidos probablemente reducen las poblaciones de Ae albopictus