Blue Ribbon Committee on Bloodborne Parasitic Diseases

In summary, the A1 recommendations are related to: developing a network (epidemiologic and demographic aspects); undertaking activities within the network; providing support for parasite research testing; developing new policies, and; preparing a Memorandum to Cabinet for submission by September 1, 2001, for funding from April 2002 over 5 years. The A recommendations deal with sustaining the network and addressing existing needs, including Public and professional education Review of current policies Business plan Development of a contribution program to meet operational needs. The B recommendation(s) will be dealt with by the future Treasury Board submission. The group identified no C recommendations.

Comparison of self-assessment and scutal index for the duration of Ixodes ricinus tick attachment

Experimental studies have shown that the efficacy of transmission of B. burgdorferi sensu lato from an infected tick to an experimental animal is significantly associated with the duration of tick attachment. Scutal index is the ratio between body length and scutum width and was found to be an objective indicator of the duration of Ixodes scapularis tick attachment, but no data for I. ricinus have been published. In this preliminary report on 30 volunteers with an attached I. ricinus tick (21 had an adult female tick and 9 a nymph), none developed any sign of Lyme borreliosis but we were able to demonstrate two asymptomatic seroconversions in a six-week follow-up period. Twenty-six (87%) volunteers claimed that they were able to determine the approximate duration of tick attachment; participants with attached adult female ticks estimated the duration of attachment to be 30 (2-90) hours, while those with attached nymphs reported 48 (18-90) hours (p = 0.681). Scutal indices were 3.2 (2-5) for nymphs and 3.2 (1-5) for adult ticks, indicating 60- and 48-hour attachment, respectively. According to the volunteers' assessment and scutal index findings, approximately 80% and 45% of adult female ticks were removed within 48 hours after the tick bite (p = 0.032), respectively, while the corresponding values for nymphs were 85% and 17% (p = 0.053). Our findings were limited by low numbers of volunteers and by the lack of experimental data on the value of the scutal index for estimation of the duration of I. ricinus tick attachment.

Prevalence of granulocytic Ehrlichiae in Ixodes ricinus ticks in Middle Germany (Thuringia) detected by PCR and sequencing of a 16S ribosomal DNA fragment

A total of 305 Ixodes ricinus ticks (243 nymphs and 62 adults) were collected from three different regions of Thuringia in Middle Germany which are known to be endemic for Borrelia burgdorferi. Our aim was to investigate the carrier rate of ticks for granulocytic Ehrlichia species. The presence of ehrlichial 16S ribosomal DNA was investigated by polymerase chain reaction. Using primers specific for the Ehrlichia phagocytophila group PCR fragments of 151 bp and 943 bp, respectively, were produced in positive samples. Adult ticks showed a significantly higher infection rate (4/62; 6.5%) compared to nymphs (3/243; 1.2%). Prevalence rates varied between 0 and 3.8% regarding the different areas under investigation. The nucleotide sequences showed high similarity (between 97.5% and 99% identity) to the known sequences of the three E. phagocytophila group members HGE agent, E. phagocytophila and Ehrlichia equi. The sequence data did not allow a final classification to a particular member of this group.

Diagnosis of epizootic bovine abortion in Nevada and identification of the vector

In the 43 years since the first description in California, epizootic bovine abortion (EBA) has been considered but not definitively diagnosed as a cause of late-term abortions on Nevada ranches. Examination of aborted full-term bovine fetuses obtained from Nevada ranches revealed gross abnormalities consistent with EBA (enlarged lymph nodes, petechial hemorrhages of the oral mucosa and conjunctiva, ascites, and splenohepatomegaly), and EBA was confirmed by histologic examination of fetal tissues. The histologic thymic changes were characteristic of EBA and included severe histocytic thymusitis with depletion of thymocytes, interlobular hemorrhage, and fibrinocellular exudation. The gross enlargement of lymph nodes was the result of cortical follicular hyperplasia and histiocytic lymphadenitis. In addition, widespread, predominately nonsuppurative histologic lesions typical of EBA were observed in most organs, including the brain, lung, heart, liver, and spleen. Furthermore, the presence of Ornithodorus coriaceus, the argasid tick vector of EBA, was established by tick collection using CO2 traps. The tick was identified on ranches and in geographic areas (northern and northwestern counties of Nevada) coincident with diagnosis of multiple cases of EBA. This study establishes the presence of EBA as a cause of late-term abortion in Nevada. Additionally, identification of the EBA tick vector, O. coriaceus, in the same areas as the abortions provides strong evidence that the disease is endemic.

Isolations of Bwamba virus from south central Uganda and north eastern Tanzania

BACKGROUND

Bwamba virus (Genus Bunyavirus, family Bunyaviridae) is widely distributed in Africa. It causes many unidentified fevers because of its benign nature.

OBJECTIVES

Samples of blood from patients were received at Uganda Virus Research Institute for diagnosis and confirmation of infections. Mosquito collections obtained in the O'nyong-nyong virus fever epidemic in Rakai in 1997 were also investigated in an effort to confirm the vectors of O'nyong-nyong virus fever.

METHODS

Patientsapos; serum and aliquots of mosquito pools were inoculated into the brain of 1-day old albino mice for attempted isolation of viruses. Positive isolates from sick mice were confirmed to be Bwamba virus by immunoflourescence assay microscopy and by plaque reduction neutralization tests.

RESULTS

Three positive isolates of Bwamba virus were obtained. One of the strains was isolated from a sample of blood from a refugee in Burigi Camp, Ngara, in north eastern Tanzania; another strain was isolated from a health worker at the Uganda Virus Research Institute, working with the Rakai Project on HIV in Rakai district; while the third strain was isolated from a pool of 50 Anopheles funestus mosquitoes collected during the O'nyong-nyong virus fever epidemic in Rakai district in 1996/1997.

CONCLUSIONS

Bwamba fever may be more common than it is usually thought to be. It is often mistaken for malaria and because it is a mild infection, many people do not go to hospital when infected. Further studies are needed to understand the epidemiology and natural history of Bwamba virus.

Epidemiologic and ecologic characteristics of some diseases transmitted by arthropods on the littoral of the Republic of Croatia

OBJECTIVE

To show epidemiologic and ecologic characteristics of some diseases transmitted by arthropods on the littoral of the Republic of Croatia.

METHODS

The pattern of infectious diseases that are transmitted exclusively by vectors was monitored during the period 1985 to 1999. Data on the incidence of the diseases in the Republic of Croatia as a whole and available data on the presence of the vectors for the diseases on the littoral are presented for comparison.

RESULTS

Mediterranean spotted fever, murine typhus, Lyme disease, cutaneous and visceral leishmaniasis, and pappataci fever occur sporadically on the Croatian littoral. Tick-borne meningoencephalitis is endemic in the northwestern part of Croatia but is not present on the littoral. Twelve cases of malaria are imported into Croatia per year on average.

CONCLUSION

Diseases transmitted by arthropods are not a major public health problem in Croatia. The medically relevant entomofauna of Croatia has not yet been adequately investigated.

[The prescription of repellents]

Repellents are chemical products designed to ward off insects. They are effective against a wide range of arthropods including mosquitoes and flies but not against bees and wasps. Choosing the proper repellent can be difficult because no single product repels all pests. This article compares the performance and toxicity of various repellents based on reports describing systemic, topical, or physical repellents made from natural or synthetic ingredients. Essential oils are the most common natural ingredient. Synthetic ingredients range from dimethyphtalate, ethylexanediol, and diethyltoluamide (DEET) to new molecules such as 35/35, piperidine, bayerepel, and KBR 3023. Our findings indicate that DEET, used as the gold standard in most studies, is still the most effective repellent. There is no synergy between any of these products but combinations (e.g. ethylhexanediol and DEET) can optimize protection. In conclusion we propose guidelines for prescribing repellents to achieve the required level of protection in function of the duration of exposure and benefit-to-risk ratio. Several recommendations are made on the safe use repellents for adults and children.

An evidence-based vector control strategy for military deployments: the British Army experience

We describe the British Army's current strategy for controlling arthropod vectors of disease during overseas deployments. Military commanders and medical officers have different, but complementary responsibilities in achieving vector control. In this paper we define a hierarchy of evidence-based vector control guidelines. Field guidelines must be based on the best available research evidence, preferably that derived from pragmatic randomised controlled trials (RCTs), and from systematic reviews of trials. Assessing the effectiveness of different vector control measures involves a trade-off between the relative benefits and harm of different technology options. There is compelling scientific evidence that bed nets and screens treated with a pyrethroid insecticide are highly effective in protecting against nocturnally active, anthropophilic arthropods (including ectoparasites), and will reduce the incidence of malaria, leishmaniasis, lymphatic filariasis and Chagas' disease. Etofenprox and deltamethrin are the safest pyrethroids, and permethrin the least safe. Vector control strategies of probable effectiveness are the use of insecticide-treated clothing, the wearing of protective clothing, and the correct use of DEET-based topical insect repellents. Aerosol insecticides are of debatable effectiveness. Other effective vector control measures, of limited usefulness during deployments, include electric fans, mosquito coils/vaporising mats, and smoke. "Biological" vector control measures, and insect buzzers/electrocuters are ineffective. Practical insect avoidance measures, based on an understanding of vector biology, complete the military vector-control arsenal. We conclude that practical insect avoidance measures, combined with pyrethroid-treated nets and clothing, and DEET-based topical repellents, can achieve almost 100% protection against biting arthropods.

Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt

The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.

The laboratory role in diagnosis of infections transmitted by arthropods

This article provides an overview of arbovirus diseases from the perspective of laboratory diagnosis and related responsibilities of health personnel. Although the disease manifestations are very diverse, general lessons relevant to optimal use of laboratory resources can be drawn from medically important examples. This approach is warranted, because under conditions of bioterrorism or emergence of a novel pathogen, ecologic clues that ordinarily facilitate identification of an arbovirus infection most likely will be absent.

Two species of tabanids (order: Diptera) in Aswan District, Egypt

Tabanus taeniola and Haematopota minuscula were trapped on camels and equines at daytime during summer of 2000. Many species of Tabanus and few species of Haematopota were reported before in Egypt. This paper stresses on the medical and veterinary importance of these vectors.

Human health improvement in Sub-Saharan Africa through integrated management of arthropod transmitted diseases and natural resources

A concept of an ecosystem approach to human health improvement in Sub-Saharan Africa is presented here. Three factors mainly affect the physical condition of the human body: the abiotic environment, vector-transmitted diseases, and natural resources. Our concept relies on ecological principles embedded in a social context and identifies three sets of subsystems for study and management: human disease subsystems, natural resource subsystems, and decision-support subsystems. To control human diseases and to secure food from resource subsystems including livestock or crops, integrated preventive approaches are preferred over exclusively curative and sectorial approaches. Environmental sustainability - the basis for managing matter and water flows - contributes to a healthy human environment and constitutes the basis for social sustainability. For planning and implementation of the human health improvement scheme, participatory decision-support subsystems adapted to the local conditions need to be designed through institutional arrangements. The applicability of this scheme is demonstrated in urban and rural Ethiopia.

Catastrophes after crossing species barriers

Probably the most tragic examples of virus infections that have caused the deaths of many millions of people in the past century were the influenza and AIDS pandemics. These events occurred as a direct result of the introduction of animal viruses into the human population. Similarly, mass mortalities among aquatic and terrestrial mammals were caused by the introduction of viruses into species in which they had not previously been present. It seems paradoxical that at a time when we have managed to control or even eradicate major human virus infections like polio and smallpox we are increasingly confronted with new or newly emerging virus infections of humans and animals. A complex mix of social, technological and ecological changes, and the ability of certain viruses to adapt rapidly to a changing environment, seems to be at the basis of this phenomenon. Extensive diagnostic and surveillance networks, as well as novel vaccine- and antiviral development strategies should provide us with the safeguards to limit its impact.

Transmission of arboviruses without involvement of arthropod vectors

Transmission of arboviruses (arthropod-borne viruses belonging to various virus families) without involvement of arthropod vectors has been documented for years, but the reports have not been reviewed systematically. The recent report of West Nile (WN) virus isolation from a hawk in mid-winter in New York (Garmendia et al., J. Clin. Microbiol. 38, 3110-3111, 2000) generated a considerable interest in this mode of arbovirus transmission. In this article, the data available worldwide are analyzed according to the factors involved in such a transmission under natural conditions, mode of infection, virus entry mechanism, administration and efficacy evaluation of vaccines, and significance in agricultural trade and public health. Analysis of numerous reports compiled for this review revealed that peroral and intranasal/aerosol transmissions are very common among arboviruses. The mechanism of virus infections in animals was most extensively studied for intranasal/aerosol infection, confirming two routes of virus spread to central nervous system (CNS), olfactory and hematogenous. To rule out the possibility of asymptomatic, cryptic infection the efficacy evaluation of candidates for vaccines against neurotropic arboviruses should include virus isolation from tissues of not only symptomatic but also of asymptomatic animals that survive intranasal virus challenge. Human activities, such as feeding livestock animals with food containing virus-contaminated meat and assembling a large number of livestock from many geographically-separated locations, have been identified as a cause of spread of some arboviral diseases. Despite numerous laboratory reports, the significance of this mode of transmission of arboviruses under natural conditions was rarely investigated, except for a few viruses important for veterinary medicine.

Pharmacological factors in the saliva of blood-feeding insects. Implications for vesicular stomatitis epidemiology

Vesicular stomatitis (VS) epizootics in the Western United States have caused substantial economic losses to U.S. livestock industries in 1995, 1997, and 1998. The role of arthropods in transmitting VS to U.S. livestock is unclear. In particular, the impact of arthropod salivary gland factors in VS infections in livestock needs study. Pharmacological effects of arthropod salivary gland factors on animals are reviewed. The potential effects of arthropod saliva on the transmission and spread of VS virus to livestock in the Western U.S. is presented with emphasis on the biting midge, Culicoides sonorensis. Information is discussed with attention to vector potential of C. sonorensis, and its use as a model for evaluating insect salivary gland pharmacology on livestock response to VS.

The many faces of Borrelia burgdorferi

In this review we describe several genetic regulatory mechanisms adopted by the agent of Lyme disease, Borrelia burgdorferi, to sense and adapt to different host and environmental conditions either in vitro or in vivo. This regulation results in the increased or decreased synthesis of several proteins whose levels are believed to play key roles in the ability of B. burgdorferi to cycle between both arthropod and mammalian hosts. Moreover, the differential synthesis of these proteins serves to modulate the response of B. burgdorferito signals in the requisite host and may also, in some cases, function as virulence determinants of this spirochete. Elucidation of these mechanisms will help in the understanding of the pathogenicity of B. burgdorferi as well as aid in identifying proteins that are important during different stages of infection.

Impact of single round of indoor residual spray with lambda-cyhalotrin 10% WP on Plasmodium falciparum infection in Akola district, Maharashtra State

Lambda-cyhalothrin 10% WP (ICON 10WP) was sprayed from 5th November 1997 at a dose of 25 mg/m2 as indoor residual spray in 74 high risk villages. The spray was completed within 10 days in most of the villages. The monthly entomological monitoring showed nil density of Anopheles culicifacies and Aedes and very low density of non-vector Anopheles and Culex. The impact of Lambda-cyhalothrin spray was discernible right in the month of November 1997 showing 52% reduction in P. falciparum cases as compared to the same month of preceding year. The reduction of P. falciparum cases in three months post-spray period was 77% (from 47 cases to 11 cases) as compared to similar months of preceding year and overall reduction of total malaria cases was 50% during the same period. Since the major part of transmission of P. vivax infection was over by the time Lambda-cyhalothrin spray was taken up, obviously the impact on P. vivax infection was not markedly high as compared to P. falciparum infection. Neither cerebral malaria cases nor deaths due to malaria were recorded in the sprayed villages.

Environmental information systems for the control of arthropod vectors of disease

Over the last decade, remote sensing technologies and geographical information systems have moved from the research arena into the hands of vector control specialists. This review explains remote sensing approaches and spatial information technologies used for investigations of arthropod pests and vectors of diseases affecting humans and livestock. Relevant applications are summarized with examples of studies on African horse sickness vector Culicoides midges (Diptera: Ceratopogonidae), malaria vector Anopheles and arbovirus vector culicine mosquitoes (Diptera: Culicidae), leishmaniasis vector Phlebotomus sandflies (Diptera: Psychodidae), trypanosomiasis vector tsetse (Diptera: Glossinidae), loaiasis vector Chrysops (Diptera: Tabanidae), Lyme disease vector Ixodes and other ticks (Acari: Ixodidae). Methods and their uses are tabulated and discussed with recommendations for efficiency, caution and progress in this burgeoning field.

Dengue/DHF: an emerging disease in India

Dengue/DHF is an emergent disease in India and some parts of country are endemic and periodically contributing annual outbreaks of dengue/DHF. Dengue infection manifests as undifferentiated fever, dengue haemorrhagic fever (DHF) which leads to hospitalization large number of people in a localized area. There is high mortality and morbidity associated with the onset of each dengue outbreak leading to great socio-economic impact. The prevention and control of dengue outbreak depends upon the proper monitoring of the disease case through disease surveillance so as to ensure timely management of cases. Vector surveillance helps in the proper and timely implementation of emergency control measures against dengue vector i.e. Aedes aegypti. There is an urgent need for an effective diagnostic strategy for early diagnosis to shorten the illness duration, hospitalization time and the associated complications.

Comments on the epidemiology, pathogenesis and control of dengue

Dengue is currently the most important viral disease transmitted to man by arthropods, whether measured by the number of cases or number of deaths. Prevalence of the disease is highest in tropical Asia, intermediate in tropical America, and lowest in tropical Africa. Four distinct dengue viruses have been identified. Types 2 and 3 appear to be more pathogenic on the average than types 1 and 4, but all four can cause severe or fatal dengue syndromes. Infection with any of the four viruses confers life-long homotypic, but not heterotypic, immunity. Dengue viruses can be transmitted by several mosquito species of the genus Aedes, but by far the most common vector is Aedes aegypti. All non-human primates that have been tested are susceptible to infection, but none exhibit signs of illness. The resulting lack of a suitable experimental host other than man has slowed progress in understanding the pathogenesis of severe forms of the disease. Controversy continues over the hypothesis that a first dengue infection increases the risk of severe disease upon re-infection as well as over the principal sites of replication. With regard to replication sites, some authors have mentioned cells of the mononuclear phagocyte lineage while others have implicated hepatocytes. No vaccine is currently available for dengue. Because the principal mosquito vector can use a wide variety of small domestic containers, vector control programs have not been highly effective.

Research ethics. Managing risks of arthropod vector research

Field research with vectors is an essential aspect of vector biology research and vector-borne disease prevention and control. This type of research, which brings experimental vector manipulations into endemic areas, can present risks to human populations. This paper seeks to stimulate a full discussion within the medical entomology community of the risks associated with vector field research. Such discussions will promote development of a consensus, among investigators, sponsoring agencies and the communities within which the work is done, so that appropriate steps can be taken to minimize and manage the risks, and adequate oversight can be maintained.