Forecast of acute respiratory infections: expected nonepidemic mobidity in Cuba

A forecast of nonepidemic morbidity due to acute respiratory infections were carry out by using time series analysis. The data consisted of the weekly reports of medical patient consultation from ambulatory facilities from the whole country. A version of regression model was fitted to the data. Using this approach, we were able to detect the starting data of the epidemic under routine surveillance conditions for various age groups. It will be necessary to improve the data reporting system in order to introduce these procedures at the local health center level, as well as on the provincial level.

The level of infestation with the vector of cattle babesiosis in Argentina

Studies were carried out to determine the differential aptitude to sustain the only vector of cattle babesiosis in Argentina, the tick Boophilus microplus, throughout the infested region of this country. Tick counts on Bos taurus cattle were used as the main criterion to classify favourable (F), intermediate (I) and unfavourable (U) areas for its development. The geographical limits of each area set up using data of non-parasitic tick stages, temperature, water balance and map recognition of flooded and unflooded zones. The F area contained 16.5 x 10 (elevado a sexta potência) ha with a cattle population of 6 x 10 (elevado a sexta potência); the I and U areas had 25 x 10 (elevado a sexta potência ha with 2.7 x 10 (elevado a sexta potência) cattle and 198 x 10 (elevado a sexta potência) with population of 2.4 x 10(elevado a sexta potência) cattle, respectively. Research on the relationship amongst Babesia-Boophilus-cattle is needed in the F area for tick development which coincides with the best region for cattle breeding.

Transmission and diagnosis of equine babesiosis in South Africa

The transmission and prevalence of Babesia equi and B. caballi are being studied. Rhipicephalus evertsi mimeticus an ixodid tick from Namibia was identified as a new vector of B. equi, however, R. turanicus, previously reported to be a vector, failed to transmit both B. equi and B. caballi in the laboratory. The accurate diagnosis of B. caballi is being investigated because the nature of its low level parasitaemia does not allow easy detection in thin blood smears, routinely used for diagnosis, by clinicians. Consequently its role as a pathogen remains obscure. The importance of identifying infected horses, destined for export to Babesia-free coutries, is also stressed. Thock and thin blood smears, serology (IFAT) and DNA probes are currently employed to study disease prevalence. To date 293 healthy, adult, throughbred horses have been screened by all three methods. The percentage positives are as follows: B. equi 4.4%, 70.6%, 13% and B. caballi 0.7%, 37%, 18.4% respectively. The DNA probes were more sensitive than blood smear examination for diagnosing carrier infections but are probably not sensitive enough to identify all carrier infections. A poor correlation was found between detection of the parasites' DNA and seropositivity. However, polymerase chain reaction could be used to amplify parasite DNA in a particular sample and its could result in more accurate diagnosis.

Transmission immunity in malaria: reflections on the underlying immune mechanisms during natural infections and following artificial immunization

Malaria transmission-blocking immunity has been studied in natural malaria infections in man, during infections in animals and following artificial immunization of animals with sexual stage malaria parasites. Effective immunity, which prevents infectivity of a malarial infection to mosquitoes, has been observed under all of these circumstances. Two general types of effector mechanism have been identified. One is an antibody mediated mechanism which acts against the extracellular sexual stages of the parasite within the midgut of a blood feeding mosquito. The other is a cytokine mediated mechanism which inactivates the gametocytes of the parasites while in the circulation of the vertebrate host. Both effects have been observed during natural infections and following artificial immunization. The basis of induction of transmission-blocking immunity, including the nature of the memory for such immunity, however, may be very different in different host/parasite systems and during natural infection of following artificial immunization. Following artificial immunization a strong immune memory for transmission blocking immunity has been observed in animal systems. By contrast, following natural infections in man immune memory for transmission blocking immunity has been found to be weak and short lived if it occurs at all. It is suggested that the immunogens which induce natural transmission blocking immunity may be CD4+ independent.

Non-immunologic methods of diagnosis of babesiosis

The diagnosis of tick-borne diseases such as babesiosis still depends on observing the parasite in the infected erythrocyte. Microscopic observation is tedious and often problematic in both early and carrier infections. Better diagnostic methods are needed to prevent clinical disease, especially when susceptible cattle are being moved into disease enzootic areas. This study evaluates two techniques for early diagnosis of Babesia bovis infections in cattle, DNA probes specific for the organism and fluorescent probes specific nucleic acid. The radioisotopically labeled DNA probes are used in slot blot hybridizations whith lysed blood samples, not purified DNA. Thusfar, the probe is specific for B. bovis and can detect as few as 1000 B. bovis parasites in 10µl of blood. The specificity of the fluorescent probe depends on the characteristic morphology of the babesia in whole blood samples, as determined microscopically. The fluorescent probe detects as afew as 10,000 B. bovis parasites in 10*l as blood. The application of each method for alboratory and field use is discussed.

Vector incrimination and effects of antimalarial drugs on malaria transmission and control in the Amazon Basin of Brazil

World ecosystems differ significantly and a multidisciplinary malaria control approach must be adjusted to meet these requirements. These include a comprehensive understanding of the malaria vectors, their behavior, seasonal distribution and abundance, susceptibility to insecticides (physiological and behavioral), methods to reduce the numbers of human gametocyte carriers through effective health care systems and antimalarial drug treatment, urban malaria transmission versus rural or forest malaria transmission, and the impact of vaccine development. Many malaria vectors are members of species complexes and individual relationship to malaria transmission, seasonal distribution, bitting behavior, etc. is poorly understood. Additionaly, malaria patients are not examined for circulating gametocytes and both falciparum and vivax malaria patients may be highly infective to mosquitoes after treatment with currently used antimalarial drugs. Studies on the physiological and behavioral effects of DDT and other insecticides are inconclusive and need to be evalusted.

V-region-related and -unrelated immunosupression accompanying infections

This paper discusses current evidence for the relationship between polyclonal lymphocyte activation, specific immunossupression with decreased resistance, and autoimmune pathology, that are all often found associated with infections by a variety of virus, bacteria and parasites . The central question of class determination of immune effector activities is considered in the context of the cellular targets for nonspecific mitogenic activities associated with infection. A model is presented to integrate these findings: mitogenens produced by the microorganism or the infected cells are preferentially active on CD5 B cells, the resulting over-production of IL-10 will tend to bias all immune activities in to a Th-2mode of effector functions, with high titers of polyclonal antibodies and litle or no production of gamma IFN and other "inflamatory"lymphokines that often mediate resistance. In turn these conditions allow for parasite persistence and the corresponding long-term disregulation of self-directed immune reactivities, resulting in autoimmunity in the chronic phase. This model would predict that selective immunization with the mitogenic principles involved in desregulation, could stand better chances than strategies of vaccination based on immunopotentiation against othere, functionally neutral antigenic epitopes. It is argued, however, that the complexity of immune responses and their regulation together with our ignorance on the genetic controls of class-determination, offer poor prospects for a scientifically-based, rational development of vaccines in the near future. It is suggested that empirically-based and technologically developed vaccines might suceed, while basic scientific approaches are reinforced and given the time provide a better understanding of those process.

Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection.

The distribution of intestinal helminth infections in a rural village in Guatemala

Fecal egg count scores were used to investigate the distribution and abundance of intestinal helminths in the population of a rural village. Prevalences of the major helminths were 41% with Ascaris lumbricoides 60% with Trichuris trichiura and 50% with Necator americanus. All three parasites showed a highly aggregated distribution among hosts. Age/prevalence and age/intensity profiles were typical for both A. lumbricoides and T. trichiura with the highest worm burdens in the 50-10 year old children. For hookworm both prevalence and intensity curves were convex in shape with maximum infection levels in the 30-40 year old age class. Infected females had higher burdens of T. trichiura than infected males in all age classes of the population; there were no other effects of host gender. Analysis of associations between parasites within hosts revealed strong correlations between A. lumbricoides and T. lumbricoides and T. trichiura. Individuals with heavy infections of A. lumbricoides and T. trichiura showed highly significant aggregation within households. Associations between a variety of household features and heavy infections with A. lumbricoides and T. trichiura are described.

Visceral leishmaniasis in Teresina, state of Piauí, Brazil: preliminary observations on the detection and transmissibility of canine and sandfly infections

A Leishmania donovani-complex specific DNA probe was usedto confirm the widespread dissemination of amastigotes in apparently normal skinof dogs with canine visceral leishmaniasis. When Lutzomyia longipalpis were fed on abnormal skin of five naturally infected dogs 57 of 163 (35 per cent) fliesbecame infected: four of 65 flies (6 per cent) became infected when fed on apparently normal skin. The bite of a single sandfly that had fed seven days previouslyon a naturally infected dog transmitted the infection to a young dog from a non-endemic area. Within 22 days a lesion had developed at the site of the infectivebite (inner ear): 98 days after infection organisms had not disseminated throughout the skin, bone marrow, spleen or liver and the animal was still serologically negative by indirect immunofluorescence and dot-enzyme-linked immunosorbent assay. When fed Lu. longipalpis were captured from a kennel with a sick dog known to be infected, 33 out of 49 (67 per cent) of flies contained promastigotes. In contrast only two infections were detected among more than 200 sandflies captured in houses. These observations confirm the ease of transmissibility of L.chagasi from dog to sandfly to dog in Teresina. It is likely that canine VL is the major source of human VL by the transmission route dog-sandfly-human. the Lmet2 DNA probe was a useful epidemiological tool for detecting L. chagasi in sandflies.

In vivo differentiation of Trypanosoma cruzi - 1. Experimental evidence of the influence of vector species on metacyclogenesis

Vector species has not hitherto been studied as influencing metacyclogenesis of Trypanosoma cruzi, while the role of the parasite strain has been frequently stressed as of dominant importance in this process. In order to fill this gap in our knowledge, metacyclogenesis was monitored in nine triatomine species. The first part of this paper presents photographs of the main and intermediate parasite stages in each vector species studied. In the second part of the study the proportional distribution of all these forms, as seen in Giemsa stained smears is summarized, thus providing an opportunity to analyze both: the length of time between the ingestion of the blood trypomastigotes and the appearance of metacyclic forms and the rates of developmental stages leading to these latter. The most remarkable observation was that metacyclogenesis rates in vivo appear to be vector dependent, reaching 50 in Rhodnius neglectus, 37 in its congener R. prolixus and being dramatically lower in the majority of Triatoma species (5 in T. sordida, 3 in T. brasiliensis and 0 in T. pseudomaculata) at the 120th day of infection. These observations suggest that through screening of different vector species it is possible to find some that are capable of minimizing or maximizing metacyclic production.

Integrated control measures against Culex quinquefasciatus, the vector of filariasis in Recife

Integrated control measures against Culex quinquefasciastus have been implemented in a pilot urban area in Recife, Brazil. About 3,000 breeding sites found within the operational area were responsible for very high mosquito densities recorded during the pretrial period. Physical control measures have been applied to cess pits before starting a series of 37 treatments of the other sites with Bacillus sphaericus strain 2362, over 27 months. In spite of the difficulties due to environmental conditions, very significant reductions in preimaginal population of C. quinquefasciatus were achieved and, as a consequence, low adult mosquito densities were maintained for a relatively long period of time. Entomological and environmental data gathered in this pilot project can contribute to design an integrated mosquito control program in Recife city.

The geographic understanding of snail borne disease in endemic areas using satellite surveillance

The current status of research on use of earth observing satellite sensors and geographic ifnormation systems for control program management of schistosomiais and fascioliasis is reviewed.