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PubMed2001

Infection by certain arboviruses among workers potentially at risk of infection.

Egyptian workers at sewage treatment plants (STPs) work and live in areas, which are highly infested with arthropods. Most of these diseases cause, febrile, influenza like illness, headache, backache, abdominal pain, and fatigue. To determine arboviral etiology in those workers, 264 serum samples were obtained from the workers in four STPs during January and October 1999. Enzyme linked immunosorbent assay (ELISA) was performed for immunoglobulins (IgG and IgM), for the detection of West Nile (WN), Sindbis (SIN), Rift Valley fever (RVF), Sandfly Naples (SFN) and Sandfly Sicilian (SFS) viruses. The results showed that (WN) has the highest prevalence (143/264, 54.14%), followed by (SFN) (58/264, 21.97%) then (RVF) (23/264, 7.95%), while, only one recent infection for each of RVF, SFS and SFN (1/264, 0.38%) and 3 persons for SIN viruses. Out of the four STPs Helwan workers' exhibited the highest infection rate for most of the studied arboviruses WN, SFN, SIN and SFS.

Animals↗
PubMed2004

Assessment of arbovirus vector infection rates using variable size pooling.

Pool testing of vector samples for arboviruses is widely used in surveillance programmes. The proportion of infected mosquitoes (Diptera: Culicidae) is often estimated from the minimum infection rate (MIR), based on the assumption of only one infected mosquito per positive pool. This assumption becomes problematic when pool size is large and/or infection rate is high. By relaxing this constraint, maximum likelihood estimation (MLE) is more useful for a wide range of infection levels that may be encountered in the field. We demonstrate the difference between these two estimation approaches using West Nile virus (WNV) surveillance data from vectors collected by gravid traps in Chicago during 2002. MLE of infection rates of Culex mosquitoes was as high as 60 per 1000 at the peak of transmission in August, whereas MIR was less than 30 per 1000. More importantly, we demonstrate roles of various pooling strategies for better estimation of infection rates based on simulation studies with hypothetical mosquito samples of 18 pools. Variable size pooling (with a serial pool sizes of 5, 10, 20, 30, 40 and 50 individuals) performed consistently better than a constant size pooling of 50 individuals. We conclude that variable pool size coupled with MLE is critical for accurate estimates of mosquito infection rates in WNV epidemic seasons.

Animals↗
PubMed1970

A multipurpose serological survey in Kenya. 2. Results of arbovirus serological tests.

Arbovirus infections are of public health interest in East Africa, where a very widespread epidemic of o'nyong-nyong fever was reported in 1959-60 and where the threat of yellow fever, present in neighbouring areas such as Ethiopia, remains. Sera collected in a serological survey in Kenya were therefore tested for antibodies against 3 group-A arboviruses (chikungunya, o'nyong-nyong and Sindbis), 6 group-B arboviruses (Zika, yellow fever, West Nile, Banzi, Wesselsbron and dengue 1), and Bunyamwera virus. The sera were examined mainly by the haemagglutination-inhibition test but a small proportion were also subjected to virus neutralization tests.The results showed that the prevalence of arbovirus tnfection varies markedly from area to area in Kenya. All types of arbovirus infections were more frequent on the coast than on the dry plateau around Kitui and the Lake Victoria area, The only exceptions were o'nyong-nyong and chikungunya, which were found to be just as prevalent on the coast as in Nyanza, where an epidemic was reported in 1959-60. Yellow fever antibodies were found to be present in about half of the people living on the coast but practically absent from the other two areas. It was concluded that the yellow fever antibodies in the coastal area must be due either to vaccination or to cross-reactions with other group-B arboviruses.

Adolescent↗
PubMedDate not supplied

Chikungunya fever as a risk factor for endemic Burkitt's lymphoma in Malawi.

The geographical and age distributions of endemic Burkitt's lymphoma (eBL), in Africa, parallel those of certain arboviruses, which include chikungunya fever. Increased incidences of antibodies to assorted arboviruses, including chikungunya, have been found in eBL sera compared to controls. An increased incidence and space-time case-clusters of eBL occurred during a chikungunya fever epidemic which were confirmed by serology and clinical observation. The present study, conducted in 1987-89, involved 108 eBL patients, and 97 local and 111 hospital controls. We examined, as hospital controls, patients with afebrile, non-malignant conditions admitted to Kamuzu Central Hospital, Malawi, during the eBL patients' first admission there. Analyses were for hospital controls and eBL patients at the end of their first admission and for local controls and eBL patients at the beginning of their third admission, about 8 weeks after the day of first admission, because of the local controls' temporal bias. Patients in case-clusters were among those seropositive for chikungunya virus, with a history compatible with arbovirus infection preceding the lymphoma, suggesting involvement of chikungunya virus in the case-clusters and a possible association between recent infection with this virus and development of the lymphoma. eBL patients were significantly more likely to be seropositive for chikungunya virus antibody (68x5%) than either hospital controls (46.8%) or local controls (50x5%) (P = 0x002 and 0x009, respectively), raising the possibility of an association between infection with an arbovirus and developing eBL in children already primed by holoendemic malaria and Epstein-Barr virus infection.

Alphavirus Infections↗
PubMed1976

Virus-enhanced modulation of cell surface antigens: effect on immune lytic susceptibility.

Monkey kidney cells, upon progressive subculture, became refractory to complement (C)-dependent immune cytolysis by anti-cell serum. Arbovirus infection restored these cells to a state of lytic susceptibility. Similar results were also abtained with antibody-dependent cellular cytotoxicity (ADCC), which is C independent. Antibodies raised against different subcultures varied considerably in lytic efficiency, indicating changing patterns of host cell expression during continous subculture. Taken together with the fact that arbovirus infection festored the lytic efficiency of all antibody preparations to the same degree suggested some form of host cell antigen re-expression as a mechanism. The results obtained in several exploratory experiments indicated that the antigenic re-expression responsible for the restoration of lysis was probably a local or selective rather than a generalized phenomenon. Thus, the amount of host cell surface antigen, measured by the use of mouse anti-cell serum and 125I anti-mouse globulin, was identical in both uninfected lytic susceptible and refractory cells, and decreased in both functional states following infection. Further, the binding of 125I concanavalin A, used to quantify surface glycoproteins, was similar in both lytic refractory and susceptible cells, and in both cases declined folowing virus infection. This result was incompatible with gross "masking" of cell surface antigens by exuberant production of surface coat material in lytic resistant cells. Finally, brief trypsinization of lytic resistant cells yielded an 8-fold increase in immune lysis, a result further consistent with local rather than generalized surface changes. The data were discussed interms of modulation of cell surface antigens affected both by repeated subculture and arboviral infection, and as a possible in vitro correlate of altered self-reactivity.

Animals↗
PubMed2002

[Impact of global climate changes on arboviruses transmitted to humans by mosquitoes and ticks].

Global warming [+0.5-0.6 degree C during the second half of the 20th century] seems a reality although climatologists did not reach a common agreement on its actual origin, and this phenomenon may still increase along the 21st century [+1.5 to 6 degrees C]. Epidemiologists are anxious at the eventual effects of the resulting climate change on the evolution of arbovirus infections transmitted to human beings by hematophagous vectors such as mosquitoes and ticks. Analysis of the literature devoted to this problem did not lead to precise conclusions and the mathematical models used seems insufficient for they take into account mainly the climatic factors and not enough the human ones. Examples of dengue, european tick-borne encephalitis and other arbovirus infections are discussed. Peculiar attention is devoted to the eventual effects of climatic changes on the hibernation process in some small mammals and the timing of bird's migrations, involved in enzootic cycles of arboviruses. It is likely that arbovirus diseases may locally extend, both in latitude and altitude, leading to outbreaks, but regressions may also occur.

Animals↗
PubMedDate not supplied

Establishment and characterization of a new continuous cell line from Lutzomyia longipalpis (Diptera: psychodidae) and its susceptibility to infections with arboviruses and Leishmania chagasi.

Embryonic tissue explants of the sand fly Lutzomyia longipalpis (Lutz & Neiva 1912) the main vector of Leishmania chagasi (Cunha and Chagas), were used to obtain a continuous cell line (Lulo). The tissues were seeded in MM/VP12 medium and these were incubated at 28 masculineC. The first subculture was obtained 45 days after explanting and 96 passages have been made to date. Lulo is composed of epithelioid cells, showed a 0.04 generations/hour exponential growth rate and population doubling time at 24.7 h. The cell line isoenzymatic profiles were determined by using PGI, PGM, MPI and 6-PGDH systems, coinciding with patterns obtained from the same species and colony's pupae and adults. The species karyotype characteristics were recognized (2n = 8), in which pair 1 is subtelocentric and pairs 2, 3 and 4 are metacentric. Lulo was free from bacterial, fungal, mycoplasmic and viral infection. Susceptibility to five arbovirus was determined, the same as Lulo interaction with Leishmania promastigotes.

Animals↗
PubMed1984

Arthropod-borne virus infections of the central nervous system.

Arthropod-borne viruses (arboviruses) are an important cause of meningoencephalitis in North America. This article considers the common features of the four major CNS arbovirus infections in this country and gives detailed descriptions of the individual virus infections.

Arbovirus Infections↗
PubMed2000

Molecular strategies for interrupting arthropod-borne virus transmission by mosquitoes.

Arthropod-borne virus (arbovirus) infections cause a number of emerging and resurgent human and veterinary infectious diseases. Traditional means of controlling arbovirus diseases include vaccination of susceptible vertebrates and mosquito control, but in many cases these have been unavailable or ineffective, and so novel strategies for disease control are needed. One possibility is genetic manipulation of mosquito vectors to render them unable to transmit arboviruses. This review describes recent work to test the concept of pathogen-derived resistance in arthropods by expression of viral genes in mosquito cell cultures and mosquitoes. Sense and antisense genome sequences from La Crosse virus (LAC) (a member of the Bunyaviridae) and dengue viruses serotypes 1 to 4 (DEN-1 to DEN-4) (members of the Flaviviridae) were expressed in mosquito cells from double-subgenomic and replicon vectors based on Sindbis virus (a member of the Togaviridae). The cells were then challenged with homologous or related viruses. For LAC, expression of antisense sequences from the small (S) genome segment, particularly full-length antisense S RNA, effectively interfered with replication of challenge virus, whereas expression of either antisense or sense RNA from the medium (M) segment was completely ineffective in LAC inhibition. Expression of sense and antisense RNA derived from certain regions of the DEN genome also blocked homologous virus replication more effectively than did RNA from other regions. Other parameters of RNA-mediated interference have been defined, such as the time when replication is blocked and the minimum size of effector RNA. The mechanism of RNA inhibition has not been determined, although it resembles double-stranded RNA interference in other nonvertebrate systems. Prospects for application of molecular strategies to control arbovirus diseases are briefly reviewed.

Animals↗
PubMed1984

Malaria, arbovirus and hepatitis infections in Macaca fascicularis from Malaysia.

Naturally occurring malaria, arbovirus infection and hepatitis in monkeys can be a hazard for the investigator and might interfere with the outcome of experiments. 63 young adult Macaca fascicularis from Malaysia were screened for these infections. About 1 year after their arrival in France, parasitaemia due to Plasmodium spp., was present in 6.4% of the animals and specific antibodies in 55.5%. 19 of 35 initially positive monkeys were tested again 2 years later. Parasitaemia was found in 1 of 4 monkeys and antibodies in 11 of 19 monkeys which were initially positive. 9 of the monkeys initially tested had low titres of antibodies to the Flavivirus genus. All animals were negative for the hepatitis B surface antigen and anti-HBc. The prevalence of IgG antibodies against hepatitis A was 46.0%. The implications in terms of control are discussed.

Animals↗
PubMed1999

Health risks of travelers in South Africa.

Large numbers of tourists visit South Africa every year. Travelers to urban areas are at little risk of contracting an infectious disease, however the adventure traveler is at increased risk. Yellow fever is not known to occur in South Africa. Malaria is endemic in Mpumalanga and KwaZula-Natal. Schistosomiasis is endemic in large parts of the country. Although rabies is found throughout the country, only a small number of human cases is reported. High risk areas are KwaZulu-Natal, the eastern Cape and Mpumalanga provinces. The incidence of human immunodeficiency virus (HIV) infection is high and counseling regarding sexually transmitted diseases is important. Sanitation of water is excellent in most large cities and towns; however travelers to rural areas should exercise caution. Arbovirus infections do occur but relatively few cases are reported. The hiker is at risk for tick bite fever and should be counseled. Since the abolition of apartheid, South Africa has been seen as an inexpensive, high quality destination by many tourists. In 1997, a total of 5,436,848 travelers from many different countries visited the country. Areas most frequently visited include Johannesburg, Cape Town, Durban, the Garden Route, Kruger National Park, KwaZulu-Natal and Pretoria. The most common reason for visiting the country was holiday (44%), followed by visiting friends and relatives (23%), business travel (27%) other (6%).1 Travelers, to the larger cities such as Johannesburg, Cape Town and Durban are at little risk of acquiring an infectious disease. The adventure traveler however is at greater risk as parts of the country are endemic for malaria, schistosomiasis, rabies, food and waterborne diseases, sexually transmitted diseases and arbovirus infections. Accidental deaths due to motor vehicle accidents and interpersonal violence are important health risks in South Africa. Travelers visiting popular attractions are at significantly lower risk. However this has never been quantified. This review aims to address the occurrence of infectious diseases and attempts to give guidelines to practitioners caring for travelers.

Communicable Disease Control↗
PubMedDate not supplied

[The species composition of mosquitoes and ticks in Armenia].

Comprehensive epidemiological, entomological, virological, and parasitological studies were conducted to examine the species composition and size of bloodsucking arthropoda (mosquitoes and ticks). A total of 64,567 mosquitoes and 45,180 Ixodes ticks were collected. Among the mosquitoes, Anopheles maculipennis was a prevalent species (81.6%). In all climatic zones, Dermacentor marginatus was the largest in number and most abundant during flag collections from cattle and plants (62.5% and 95.5%, respectively). Virological studies of the collected field material identified 125 strains of arboviruses belonging to 10 viruses: Tyaginya, Sindbis, Batai, Dkhori, tick-borne encephalitis, West Nile fever, Tamdy, KGL, Geta, and Bkhandzha. The identified arboviruses are environmentally associated with both mosquitoes and ticks. The larger number and diversity of bloodsucking artropoda present a potential risk of outbursts of arbovirus infections on the territory of the republic.

Animals↗
PubMed1976

Febrile illnesses resulting in hospital admission: a bacteriological and serological study in Jakarta, Indonesia.

A study of 741 Indonesian patients with fever was carried out in order to determine what serious febrile illnesses are prevalent in Jakarta. All patients were hospitalized primarily because of fever and were studied by bacteriological and serological methods. Bacteremia due to Salmonella typhi (150 cases), S. enteritidis (36 cases), or both (2 cases) was common in both children and adults. One S. enteritidis isolate was chloramphenicol resistant. Serological evidence of Salmonella infection was found in 130 additional cases without bacteremia. Serological evidence of arbovirus infection (94 cases) was common in children. Malaria was found in 12 adults, most of whom were probably infected outside Jakarta. Little serological evidence was found for rickettsial, leptospiral, Brucella, Toxoplasma gondii or a number of other infections. Clinical signs and symptoms in the febrile patients studed were generally nonspecific, and laboratory results reported were very helpful in establishing more accurate diagnoses.

Arbovirus Infections↗
PubMed1977

Arbovirus isolations from, and serological studies on, wild and domestic vertebrates from Kano Plain, Kenya.

Arbovirus infection and presence of haemagglutination-inhibiting antibodies in small mammals, birds and livestock were examined over a period of five years on the Kano Plain in western Kenya. Eleven isolations were made from mammals and birds. The viruses were identified as Arumowot and Germiston while three different agents could not be shown to be related to 188 African arboviruses. Prevalence of antibodies against arboviruses suspected of occurring in the area was generally low.

Animal Population Groups↗
PubMed1993

Seroepidemiology of dengue and other arboviruses in a natural population of toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka.

A seroepidemiological study of arboviruses infecting 115 wild toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka showed a high prevalence of antibodies to dengue and Lumbo viruses. There was low seroprevalence of Chandipura (2/115) and Batai (1/115) virus antibodies, but no seropositivity to Chikungunya or Sindbis. There was no serological evidence of infection by Japanese encephalitis (JE) virus in spite of large human epidemics in the study area, indicating that toque macaques are unlikely to be an epidemiologically relevant host in the maintenance cycle of JE virus.

Aedes↗