An outbreak of Plasmodium vivax malaria occurred in Trinidad some 25 years after a successful eradication programme. The 'index case' was infected while visiting Perdaneles, Venezuela, and was responsible for the renewal of malaria transmission by indigenous Anopheles aquasalis mosquitoes in Icacos, Trinidad, W.I. Nine cases (four females and five males) of P. vivax malaria were locally transmitted in Icacos. Most of the cases (70%) were in the 15-24 or 25-44 year age groups. In Granville/Chatham, another, unrelated case of locally transmitted P. vivax malaria was discovered through active surveillance. The intervention measures adopted, which successfully eradicated P. vivax malaria from Trinidad, are described. The need to maintain malaria surveillance is emphasized.
This review focuses on arborviral infections associated with California serocomplex (Bunyaviridae, Orthobunyavirus). Results of relevant eco-epidemiological and clinical studies in Russia are presented suggesting the ubiquitious nature of diseases caused by viruses of the California encephalitis serocomplex (Inko, Tahyna, Snowshoe Hare). The etiologic structure of these diseases in taiga and mixed woods of the European part and Western Siberia is dominated by the Inco virus and in southern regions by Tahina. The diseases have a well apparent seasonal pattern (July-August) in agreement with the peak summer activity of the pathogens. Two clinical forms of pathology are distinguished, influenza-like and generalized, the latter affecting lungs, kidneys, liver, and CNS. The Inco virus plays a key role in pathogenesis of the generalized form affecting CNS.
The introductory part has summarized the role of malaria in the course of history and various attempts of its eradication in Croatia before the World War I. Furthemore, there is a list of activities and results accomplished between 1922 and 1927 on the island of Krk by Dr. Otmar Trausmiller. After a systematic sanitation of all anopheles habitats, primarily natural and artificial bodies of still water, and introduction of imported gambusia to those bodies of water, anopheles was virtually eradicated on the island. What followed was an evident decrease of new malaria incidents, and in the campaign against malaria there was still major concern in the form of chronic patients and intensive quinine therapy. Today, about eighty years after it was introduced to Krk, gambusia still abides in ponds across the island and it represents one of the main factors in the protection against potential revival of indigenous malaria.
The success of regional networks to provide incentives and mechanisms for sharing information is illustrated through the North American Regional Action Plan on DDT (NARAP). This NARAP was designed to reduce human and environmental exposure to DDT and its metabolites in North America through cooperative efforts. The increasing role of environmental concerns in the planning and design of Mexico's DDT phase-out program motivated the Mexican Ministry of Health to undertake an alternative program for malaria control maximizing community participation without negatively affecting human and ecosystem health. This program relies on: 1) elimination of parasites in people, 2) improvement of personal and household hygiene, and 3) use of environmental management practices to eliminate mosquito breeding sites. This new strategy resulted in the elimination of DDT for malaria control in Mexico in the year 2000. While malaria and its corresponding vectors show considerable variability within a single country and certainly around the globe, the case example of Mexico provides a methodology for developing alternatives to DDT.
This study was undertaken to determine the duration of the possible malaria transmission season by the local anopheline species in the region of the town of Sandanski, situated in South-Western Bulgaria, where 18 indigenous cases of vivax malaria were recorded in the adjacent-villages in 1995-1996. The present study was conducted in the same villages in 2003 and 2004 during the potential malaria season (April-October) in Bulgaria. A total number of 758 female mosquitoes were captured and examined. The catch comprised Anopheles maculipennis Meigen (95.1%), An. sacharovi Favre (2.4%), and An. claviger Meigen (2.5%). Their physiological age was determined by the ovariolar method using the oil injection technique. The malaria transmission season was estimated to begin on May 10 in 2003 and on June 8 in 2004. In both 2003 and 2004, potentially hazardous females were found in the mosquito population in the mid-June and disappeared in the second decade of September. The beginning of the possible malaria transmission season in the region of the area of the town of Sandanski is considered to be associated with the actual appearance of potentially dangerous females in the local mosquito population. Thus, the duration of this season as determined by the age composition of the mosquito population was shorter than that determined on the basis of the mean diurnal temperatures. A sample seasonal curve of the minimum potentially dangerous physiological age of the female mosquitoes was derived from the climatic data. It is proposed to be used together with the age composition data for estimation of the actual limits of a malaria transmission season.
DPE-28, a substituted diphenyl ether (2,6-ditertiarybutyl phenyl-2',4'-dinitro phenyl ether) was reported to exhibit promising insect growth regulating activity against Culex quinquefasciatus, the vector of lymphatic filariasis. A controlled release formulation (CRF) of DPE-28 has been developed to control Cx. quinquefasciatus in its breeding habitats. Toxicity of DPE-28, safety to non-target mosquito predators and the release profile of the CRF of DPE-28 are studied and discussed.
The acute oral and dermal toxicity was tested in male and female Wistar rats as per the Organization for Economic Cooperation and Development (OECD) guidelines 425 and 402 respectively. The toxicity of DPE-28 to non-target predators was tested as per the reported procedure from this laboratory. The CRF of DPE-28 was prepared by following the reported procedure developed at this laboratory earlier. The concentration of DPE-28 released from the CRF was monitored by HPLC by constructing a calibration graph by plotting the peak area in the Y-axis and the concentration of DPE-28 in the X-axis.
DPE-28 has been tested for acute oral toxicity and found to be moderately toxic with LD 50 value of 1098 mg/kg body weight (b.w). The results of the acute dermal toxicity and skin irritation studies reveal that DPE-28 is safe and non-irritant. DPE-28 when tested at 0.4 mg/litre against non-target mosquito predators did not produce any mortality. The release profile of the active ingredient DPE-28 from the CRF by HPLC technique showed that the average daily release (ADR) of DPE-28 ranged from 0.07 to 5.0 mg/litre during first four weeks. Thereafter the matrix started eroding and the ADR ranged from 5 to 11 mg/litre during the remaining 5 wk. The cumulative release of active ingredient showed that > 90 per cent of the active ingredient was released from the matrix.
The controlled release matrix of DPE-28 was thus found to inhibit the adult emergence (>80%) of Cx. quinquefasciatus for a period of nine weeks. The CRF of DPE-28 may play a useful role in field and may be recommended for mosquito control programme after evaluating the same under field conditions.
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Cites: Pest Manag Sci. 2004 Jul;60(7):685-9015260300
Bacillus thuringiensis subsp. israelensis (Bti) is a soil-borne bacterium affiliated to the Bacillus cereus group (Bcg) and has been used in biocontrol products against nematoceran larvae for several decades. However, knowledge is limited on whether long-term Bti application can affect the structure of indigenous communities of Bcg and the overall abundance of Bti. Using species- and group-specific quantitative PCR assays, we measured the Bcg- and Bti-abundances in riparian wetlands in the River Dalälven floodplains of central Sweden. On five occasions during one vegetative season, soil samples were collected in alder swamps and wet meadows which had been treated with Bti for mosquito larvae control during the preceding 11 years, as well as in untreated control sites and well-drained forests in the same area. The average abundance of Bcg in alder swamps was around three times higher than in wet meadows. Across all sites and habitats, the Bti treatments had no effect on the Bcg-abundance, whereas the Bti-abundance was significantly higher in the treated than in the control sites. However, for individual sampling sites, abundances of Bti and Bcg were not correlated with the number of Bti applications, indicating that added Bti possibly influenced the total population of Bti in the short term but had only a limited effect in the longer term. The findings of this study increase the understanding of the ecology of Bti applications for mosquito control, which can facilitate environmental risk assessment in connection with approval of microbiological control agents.