TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE (2001) 95,244-249

Royal Society of Tropical Medicine and Hygiene Meeting at Manson House, London, 7 December 2000

Research in progress: short presentations

Oral presentations*

Interactions in vitro of Plasmodium berghei ooki- netes with components of murine basement mem- brane

Romanico Arrighi and Hilary Hurd Centre for Applied Entomology and Parasitology, School of Life Sciences, Huxley Building, Keele University, Keele, Staf- fordshire ST.5 5BG, UK

We are investigating how malaria ookinetes interact with the mosquito basement membrane and whether specific parasite surface molecules are responsible for binding and subsequent transformation to oocysts. The major components of midgut basal membranes, col- lagen, laminin and tibronectin, may be involved. Mature Plasmodium berghei ookinetes, produced in vitro, were seeded into microtitre wells that had been coated with membrane components. Following incubation at 19°C for 12 h, the plates were washed and the bound ookinetes were counted. In addition, ookinetes were preincubated with the 13.1 monoclonal antibody to Pbs21 to deter- mine the role of this surface protein in binding to the basement membrane. Finally, we used a Western blot to determine whether collagen or laminin bind to Pbs2 1. The binding studies show significant interaction between the parasite and collagen and laminin, and the inter- action is strongly blocked by the anti-Pbs21 antibody. The Western blots show binding occurs between the parasite and both components. The binding molecule appears to be the major ookinete surface protein, Pbs21.

Rapid detection of active and latent Mycobacter- ium tuberculosis infection in HIV-infected Zam- bians by enumeration of RDl gene product- specific T cells

A. L. N. Chapman’, M. MunkantaZ, K. A. Wilkinson’, A. A. Pathan’, K. Ewer’ , H. Ayles’, A. Mwinga2, I’. Godfrey-Faussett’ and A Lalvani’ . ‘Nuffield Department of Medicine, Univer- sity of Oxford, John Radcltffe Hospital, Oxford, UK; ‘ZAMBART Project, Department of Medicine, University Teaching Hospital, Lusaka, Zambia

The diagnosis of active or latent Mycobacterium tuber- culosis infection can be difficult to establish in HIV- positive individuals, resulting in difficulties in targeting antituberculous therapy and prophylaxis. We evaluated an ex-vivo interferon-y ELISPOT assay for the detection of active and latent M. tuberculosis infection in Lusaka, Zambia. T cells specific for peptides derived from ESAT- 6 and CFP-10, 2 M. tuberculosis-specific antigens en- coded by the RDl genomic segment, were enumerated. Subjects included 50 Zambian tuberculosis (TB) pa- tients, 75 healthy Zambian adults and 40 healthy UK residents. 100% (n = 11) and 90% (n = 39) of HIV- negative and HIV-positive TB patients respectively had circulating ESAT-G/CFP-1 O-specific T cells. 69% (n = 54) and 43% (n = 2 1) of HIV-negative and HIV-positive healthy Zambian adults had positive assays, compared to none of the UK controls. 80% of HIV-negative, and 36% of HIV-positive healthy Zambian adults had positive tuberculin skin tests (10 mm, 5TU).

Thus the ESAT-6/CFP-1 O-based ELISPOT assay

* [All oralpresentations not awardedprizes were highly commended.]

reliably detects active M. tuberculosis infection in this area of high TBMIV endemicity, and is more sensitive than the tuberculin skin test in the diagnosis of latent M. tuberculosis infection in HIV-positive individuals. This assay provides an accurate estimate of the prevalence of latent M. tuberculosis in this population.

[This oral presentation was awarded first prize at the meeting.]

Leptospirosis outbreak following an international sports event, Sabah, Borneo

C. Easmon Hospitalfor Tropical Diseases Travel Clinic, Capper Street, London WClE 6AU, UK

International sports events lead to large groups from different countries meeting in a single overseas location. One such event is the annual Eco-Challenge which requires teams to run, cycle and swim in difficult terrain and climatic conditions: 300 participants competed in the forests of Borneo. The Hospital for Tropical Diseases (HTD), London, first became aware of 4 returned UK participants who had symptoms suggestive of leptospiro- sis in September 2000. Leptospirosis is a bacterial in- fection caused by exposure to water contaminated with the urine of infected rats. At the time, HTD was piloting involvement in a global travel health surveillance system for travel clinics (GeoSentinel). The 4 HTD cases were immediately notified, via e-mail, to the co-ordinator of the GeoSentinel network (26 clinics worldwide). The aim was to (i) identify other cases in other countries and (ii) acquire serological confirmation. Both aims were achieved within 24 h. The Communicable Disease Con- trol Center in Atlanta, USA, identified leptospirosis 2 days prior to serological confirmation in the UK. In total over 50 cases (17% of participants) were identified worldwide as acquiring leptospirosis from Borneo. The internet and GeoSentinel aided early diagnosis, interna- tional collection and analysis of data on this outbreak.

Evaluation of the efficacy of carbosulfan- and permethrin-impregnated curtains against Ano- pheles gambiae in a village in Burkina Faso, West Africa

C. Fanello’, E. Sanogo-Ilboudo2, N. Cuzin- Ouattara2, A. Badolo’ and C. Curtis’ ‘London School of Hygiene and Tropical Medicine, Keppel Street, London WCIE 7HT UK; ‘Centre Nationale de Recherche et Formation sur le Paludisme, 01 BP 2208 Ouagadougou 01. Burkina Faso

Pyrethroid resistance is a serious threat to the con- tinued success of impregnated bednets and has been reported in the main malaria vector Anophelesgambiae S.S. in several West African countries (CHANDRE, F. et al., 1999: Bulletin of the World Health Organization, 77,230- 234). In Ivory Coast, KOLACZINSKI, J. et al. (2000: Bulletin of Entomological Research, 90, 125 - 132) showed that a carbosulfan-impregnated bednet performed sig- nificantly better than pyrethroid-impregnated bednets. Because of concerns about possible toxicity, carbosulfan treatment of curtains may be preferable and such cur- tains were compared with permethrin-treated curtains for preventing house entry by mosquitoes, as measured

SHORT PRESENTATIONS 245

by indoor light traps. The trial was carried out in a village near Ouagadougou, Burkina Faso, in the wet season of 2000. Fifteen houses were provided with curtains (car- bosulfan 0.2 g/m2 , permethrin 1 g/m2 or untreated). Five houses without curtains were used as controls. In about 60 trap-nights per treatment 1269-4437 An. gum&e xl. were caught. The percentage reduction in geometric mean count, compared with no nets, was 48.8% for untreated nets (P = 0.015), 64.2% forperme- thrin (P< 0.001) and 84.4% for carbosulfan (P < 0.001). Regression analyses showed that permethrin did not perform significantly better than untreated curtains (P = 0.141) whereas carbosulfan did perform significantly better than untreated and permethrin- treated curtains (P< O*OOl).

[This oral presentation was awarded second prize at the meeting.]

The efficacy of different mosquito trapping meth- ods in a forest-fringe village, Yunnan Province, southern China

S. J. Moore’, Zhou Hongning2 and Nigel Hill’ ‘London School of Hygiene and Tropical Medicine, Keppel Street, London WCIE 7HT UK; ‘Yunnan Institute ofMalaria Control, Simao 665000, PR China

Despite a control programme, malaria incidence in Yunnan is increasing. Population movements for social and cultural reasons expose non-immunes to high trans- mission areas. Transmission also occurs within forest- fringe villages. The vectors Anopheles dir-us and An. minimus are species complexes, exhibiting behavioural variations. Knowledge of vector bionomics is needed for efficient control. Multidrug-resistant Plasmodium falci- par-urn necessitates alternatives to human landing catches. CDC light traps with UV or ordinary incandes- cent bulbs were used for 57 trap-nights: 2703 mosquitoes were caught, comprising the vector species An. minimus and An. sinensis and the suspected vector An. maculatus. Larval An. dirus were found around the village but no adults were trapped. UV light traps caught more mos- quitoes than the incandescent traps, but were non- specific and unpopular with villagers. Traps placed in living areas ofhouses caught more mosquitoes than those placed beside bednets, and the catch comprised more species that were active in the early evening. Evans’ traps hung outdoors baited with CO, caught few mosquitoes. CDC traps in the same position baited with CO2 caught large numbers of Culex tritaeniorhynchus. Indoor spray catches recovered human-fed An. vugus and An. mini- mus.

This work confirmed that CDC light traps could be used to trap local vectors, and the abundance of early active mosquitoes in the living area suggests that personal protection measures may be required in the evening, to supplement bednet use.

Platelet-mediated clumping of Plasmodium fdci- parum-infected erythrocytes: a novel adhesive phenotype associated with severe malaria

A. Pain’, D. Ferguson’, 0. Kai3, M. Mosobo3, K. Marsh3 and D. J. Roberts’,2 ‘IMMand “NBS, John Radcltffe Hospital, O<ford OX3 9DI/, UK; 3KEMRI, PO. Box 230, Kilifi, Kenya

The diversity of adhesive phenotypes expressed at the surface of Plasmodium falciparum-infected erythrocytes has suggested particular phenotypes are associated with severe disease. Previously, we have shown that some Z? falciparum clones or lines form apparent auto-aggluti- nates of infected erythrocytes in non-immune serum and showed that this phenotype is associated with severe malaria. We have now established that such apparent

auto-agglutinates are actually clumps of infected ery- throcytes and platelets. Furthermore, platelets lacking surface expression of CD36 do not support platelet- mediated clumping. Finally, we have shown that platelet- mediated clumping is commonly expressed by field l? falciparum isolates in Kenya and is associated with severe malaria, using multinomial regression analysis [P = 0.035, OR2.19 (95% CI 1.18-4.07)]. Definingthe fine specificity of binding by the clumping parasite lines on platelet CD36 and elucidating the role of such platelet- mediated clumps would be of particular interest to understand malaria patho-physiology and define new pathways to intervene in prevention or treatment of malaria.

Systematics and population structure studies of cryptic species within Anopbeles minimus com- plex in Viet Nam, Laos and Kampuchea

H. K. Phuc and H. Townson Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK

Evidence of pre- and post-mating reproductive isola- tion mechanisms between 2 species of the malaria vector Anopheles minimus A and C has been obtained from population studies based on Odh isoenzyme, ITS2 diagnostic PCR markers and from studies of the progeny of laboratory crosses.

Eleven mitotic sex chromosome polymorphisms were observed, 5 of species A and 6 of species C. Mitotic chromosome studies on hybrids from laboratory crosses (A X C) have evaluated accurately the length correlation of autosome and sex chromosome between species A and C, indicating shortcomings of previous studies (BAIMAI et al., 1996: Journal of the American Mosquito Control Association, 12, 97- 105).

The enzymatical marker Odhl17, formerly consid- ered as evidence for species D (Green, unpublished data), is now seen to be a polymorphism within species A. The number of teeth on the larval mental plate was previously used to discriminate A from B in southern China (Yuan, Y., 1987: Mosquito Systematics, 19, 143- 145). These studies show it to have no value in the discrimination of species A and C.

Considerable divergence between these A and C has also been found in mitochondrial COI, ND3, ND4, ND5 gene sequences. These data are being used, in conjunction with microsatellite studies, to answer ques- tions about An. minimus population structure in Viet Nam, Laos and Kampuchea.

Determinants of Plasmodium fdciparum gameto- cytaemia among patients presenting at the Hospi- tal for Tropical Diseases, London, UK

M. P. Rayco-Solon’, M. Armstrong’, P. L. Chiodini3, R. Behrens’ and T. Doherty’ ‘Depart- ment of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WCIE 7HT UK; ‘Hospital for Tropical Diseases, London, UK; 3Department qf Parasitology, Hospital for Tropical Diseases, London, UK

This was a retrospective study of patients diagnosed with Plasmodium falciparum malaria at the Hospital for Tropical Diseases, London, to determine factors asso- ciated with gametocytaemia among this population. Demographic, clinical and travel data were collected from 580 patients from December 1994 to May 2000 by completing a malaria database form on discharge. Fifty- four percent of the patients originated from malarious areas; 465 (80%) were currently residing in non-malar- ious areas. The patients were mainly black Africans (270, 47%) or whites (154,27%).

Seventy-eight (13%) had patent gametocytaemia on

246

initial presentation. The patients’ ages ranged from 1.6 to 79 years, with a mean age of 37 years. Gametocytaemia was not associated with the age or gender of the patient. The strong direct association of gametocytaemia with length of illness (AOR = 4.69, P < O*OOl for 5-9 days; AOR = 5.79, P < 0.001 for >9 days), and its inverse association with high-grade fever (AOR = 0.01, P = O-026), and normal haemoglobin (AOR = 0.24, P < 0.00 1) argue strongly for the relationship between game- tocytaemia and a protracted disease. Other variables that were significant independent risk factors for gametocy- taemia include the use of chemoprophylaxis (AOR = 2.15, P = 0+021), a normal platelet count (AOR = 4.40, P < O.OOl), and non-admission to the hospital (AOR = 0.28, P = 0*039)-factors that are also compatible with mild prolonged disease. Five or more days of symptoms, anaemia, and normal temperature predicts gametocytaemia with a sensitivity of 100% and specificity of 81.4%. The observation that gametocytae- miawasalsosignificantlyassociatedwiththelengthofstay in a malarious area (AOR=2*66, P = 0.006 for stay >6 weeks) is consistent with the possibility that patients with previous exposure to malaria tend to produce gameto- cytes, suggesting that gametocytogenesis may at least be partially mediated by the patient’s immune response.

Audit project of paediatric patients with Mycobac- terium tuberculosis managed by the Royal London Hospital, Whitechapel, and the London Chest Hospital between 1998 and 1999

A. Samarasinghe Department of Public Health, KCW Health Authority, London W2 6LX, UK

There is emerging evidence of paediatric cases of Mycobacteriuvn tuberculosis infection occurring in patients born in the UK, who have parents of Indian-subconti- nent origin (DAVIDSON, R. N., 2000: Transactions of the Royal Society of Tropical Medicine and Hygiene, 94, 5-6). This project examines the paediatric population served by the Royal London Hospital, Whitechapel, and the London Chest Hospital between 1998 and 1999 who were diagnosed with M. tuberculosis, in order to establish their ethnicity, whether they were managed in shared care, whether a recommended treatment regimen was used, which team followed-up these cases, and also what proportion of patients completed their treatment and underwent contact tracing.

A synthetic antimicrobial peptide based on Aedes aegypti defensin B exhibits antimicrofilarial activ- ity in vitro

C. Strode and H. Townson Liverpool School of Tro- pical Medicine, Pembroke Place, Liverpool L3 SQA, UK

Antimicrobial peptides are a potent part of the insect immune system and may influence the outcome of parasitic infections in mosquitoes. A synthetic antimi- crobial peptide based on Aedes aegypti defensin B significantly reduced the motility in vitro of microfilariae of the nematodes Brugia malayi and B. pahangi. Activity

Poster presentations

SHORTPRESENTATIONS

was within physiological concentrations of defensin found naturally in the mosquito, 25 pi (ALBUQUER- QUE, C. M. R. & HAM, P. J., 1996: Medical and Veterina y Entomology, 10, 397-399).

Defensin was also tested against Acanthocheilonema viteae, 1 of only 2 filarial nematode species that do not possess the intracellular bacterium Wolbachia. The tar- geting of Wolbachia has recently been shown to be the basis of tetracycline antifilarial activity (HOERAUF, A. et al., 1999: Journal of Clinical Investigation, 103, 1 l- 18) and A. viteae was included in the study so as to determine whether defensin activity against microfilariae was due to its effect on Wolbachia, as is the case with tetracycline. This proved not to be so as defensin showed significant activity and more or less equal potency against all 3 nematode species tested, irrespective of the presence or absence of Wolbachia.

Current investigations are underway to determine the killing mechanism of defensin against microlilariae and the activity profile of defensin against a number of other parasitic and pathogenic microbial organisms.

Untreated maternal syphilis and pregnancy out- come in Mwanza Region, Tanzania

D. L. Watson-Jones’, M. Rusizoka’, J. M. Changalucha3, H. Weiss’, L. Ndeki4, J. Todd’, D. Ngeleja’, R. Hayes’ and D. M. Mabey’ ‘London School of Hygiene and Tropical Medicine, London, UK; ‘Regional Medical Office, Mwanza, Tanzania: 3National Institute for Medical Research, Mwanza, Tanzania; 4Municipal OfJice ofHealth, Mwanza, Tanzania; ‘Sengerema Designated District Hospital, Sengerema, Tanzania

Estimates of the impact of maternal syphilis on preg- nancy outcome in sub-Saharan Africa have given widely disparate results (SCHULZ, K. F. et al., 1987: Genitour- inay Medicine, 63,320-325; GREENWOOD, A. M. et al., 1992: Journal of Infectious Diseases, 166, 842-846). As part of a study on antenatal syphilis screening in Mwanza Region, Tanzania, the proportion of adverse pregnancy outcomes attributable to syphilis was determined by comparing outcomes in women with and without ser- ological evidence ofuntreated syphilis at delivery. RPR+ women and the next 2 RPR- women screened on admission were recruited. Of 147 RPR+ women, 50% had active syphilis (RPR titre 21:8, TPHA+/FTA+) and 26% had a biological false-positive RPR test. Preg- nancy outcomes in women with active syphilis compared to seronegative women were: stillbirths 25% vs 1% (RR 19.1, P< 0.001); prematurity 20% vs 3% (RR 6.5, P < O*OOl); low birthweight due to intrauterine growth retardation 13% vs 7% (RR 1.8, P= 0.16). Overall, adverse pregnancy outcomes were seen in 49% of the women with syphilis, and 44% of stillbirths and 20% of premature deliveries were attributable to maternal sy- philis in this population. Untreated maternal syphilis is still strongly associated with adverse pregnancy out- comes, especially stillbirth, in this region of Tanzania. This emphasizes the importance of establishing and taking steps to maximize the use of antenatal syphilis screening programmes.

Effect of malaria infection on vitellogenin mRNA abundance in Anopheles gambiae

Ashraf M. Ahmed’, Rhayza Maingon’, Patricia Romans2 and Hilary Hurd’ ‘Centre for Applied En- tomology and Parasitology, School of Life Sciences, Keele University, Staflordshire ST5 SBG, UK; ‘Department of Zoology, University of Toronto, Ontario M5S 3G5, Canada

Malaria parasites affect the fecundity of several species of mosquito vector. We have begun to investigate the underlying mechanisms by studying the effect of the rodent malaria parasite, Plasmodium yoelii nigerimsis, on vitellogenesis in Anopheles gambiae during 2 gonotrophic cycles following an infective blood meal. Vg mRNA normally appears l-2 h post-blood meal (PBM), peaks between 24 h and 36 h and terminates after 48 h PBM.

SHORT PRESENTATIONS

Vg mRNA levels quantified using Northern blotting showed no significant differences in the Vg mRNA abundance between non-infected and infected female mosquitoes during the first gonotrophic cycle, when ookinetes were penetrating the midgut and transforming into oocysts. However, in the second gonotrophic cycle, when oocysts were developing, Vg mRNA levels were reduced in infected mosquitoes at 2, 8, 12 and 24 h PBM. This finding suggests that down-regulation of Vg mRNA transcription and/or abundance may contribute to fecundity reduction when oocysts are developing but not during earlier stages of infection.

Cat allergen levels in dust in Kuwait

M. Al-Mousawi’, H. J. Lovel’, A. A. Al-Bader’, N. Behbehani2, A. R. Al Dowaisan3, N. Arithodzic3, M. Craven4, A. Custovic4 and A. Woodcock4 ‘School of Primary Care, University of Manchester; Man- chester Ml4 5NP UK; 2Kuwait Health Sciences Centre, Kuwait; 3Al Rashid Allergy Centre, Kuwait: 4NW Lung Centre, Wythenshawe Hospital, Manchester M23 9LT UK

Cat allergy is a known risk factor for asthma in devel- oped countries (CUSTOVIC, A. et al., 1998: Thorax, 53, 33-38), where cat allergen is ubiquitous and found in dust in public places and in homes with and without cats. Dust samples were collected in Kuwait from 73 public places and 357 homes (123 households with a child with asthma and 234 controls). The mean concentration of Fe1 d 1 found in the dust samples in public places was 0.55 mg/g, and in caticatless households 1.97,’ 0.22 mg/g in living rooms and 2,38/0.50 mg/g in bed coverings. These concentrations appear lower than UK levels (CUSTOVIC, A. et al., 1998: Thorax, 53, 33-38, 1998: Clinical andExperimentalAllergy, 28, 53-59). The importance of cat allergy in childhood asthma in Kuwait is currently being assessed in a case-control study.

Partial cross-resistance to carbosulfan of pyre- throid-resistant strains of Anopheles

A. N. Asidi and C. F. Curtis London School of Hygiene and Tropical Medicine, Keppel Street, London WClE 7HT, UK

Pyrethroid resistance is a serious threat to the con- tinued usefulness of insecticide-treated nets to control malaria vectors. It is therefore important to investigate alternative insecticides. Encouraging results have been achieved with the carbamate carbosulfan in C&e d’Ivoire where Anopheles gambiae has a high frequency of the kdr pyrethroid-resistance gene (KOLA~ZIN&I, J. et al., 2000: Bulletin of Entomological Research. 90. 125 - 132).

The present laboratory investigation was on the in- secticidal and irritant effect of carbosulfan on pyrethroid- resistant strains of An. gambiae originating from Burkina Faso (West Africa) and An. stephensi from Dubai and on susceptible strains of each species. The mosquitoes were exposed to nets with doses of carbosulfan ranging from 12.5 to 400 mg/m2 and were re-tested at 3 and 6 months. There was little variation with dose or age of net in mortality or irritancy, as measured by time for first take- off. However, both pyrethroid-resistant strains showed reduced irritancy compared to the susceptible strains in response to carbosulfan. Both pyrethroid-resistant strains, especially the Dubai strain, showed partial cross-resistance, in terms of mortality, on carbosulfan.

PCR and RFLP-based serotyping of Streptococcus pneumoniae

S. L. Batt, B. M. Charalambous and S. H. Gillespie Department of Medical Microbiology, Royal Free and University College Medical School, Royal Free Campus, London NW3 ZQG, UK

Lower respiratory-tract infections annually cause more than one million deaths in African under-fives, with Streptococcus pneumoniae being the main pathogen. We are conducting a longitudinal and cross-sectional study of carriage in northern Tanzania. Serotyping is increasingly important with advent of the new conjugate vaccine, which may alter the epidemiology of common invasive serotypes. We are developing a PCRRFLP- based serotyping technique, targeting CpsA and CpsB portion of the capsulation locus (LAWRENCE, E. et al., 2000: Journal of Clinical Microbiology, 38, 13 19- 1323). Preliminary studies show that this technique is able to distinguish common serotypes. Furthermore PCR of isolated DNA from groups A and C streptococci, viridans streptococci, Haemophilus influenzae, coagu- lase-negative and Oxford staphylococci, Escherichia coli, Pseudomonas aeruginosa, yeast and Mycobactet-ium tuber- culosis suggests that this PCR is sufficiently specific to be applied directly to primary specimens. We present the above PCR and RFLP data including evidence that it may detect multiple colonization.

Mitochondrial DNA variation within and among populations of mosquitoes of the Aedes scutellaris complex in relation to Wolbachia infection

A. Behbahani, H. Townson and S. P. Sinkins Par- asite and Vector Biology Division, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 SQA, UK

The Aedes scutellaris complex is important because some members of the group are important vectors of subperiodic Wuchereria bancrofti, the agent of bancrof- tian tilariasis in the South Pacific. On the other hand, some members show maternally inherited incompati- bility (MEEK, S. R., 1988: In: Biosystematics of Haema- tophagus Insects, Service, M. W. (editor), pp. 115-132) which is caused by Wolbachia, a maternally inherited bacterium.

Wolbachia would be expected to reduce mitochondrial diversity when it spreads into populations. In this study haplotype diversity of mitochondrial genes such as COI, CO11 and ND5 was examined in members of the Ae. scutellaris group: Ae. polynesiensis from Fiji which is Wolbachia infected and Ae. katherinensis which is Wolba- chia uninfected.

An experimental evaluation of the genetic control theory for schistosomiasis

L. Blair’, J. P. Webster’, C. M. Davies’ and M. Doenhoff t Wellcome Trust Centre for the Epidemi- ology of Infectious Disease, Department of Zoology, Uni- versity of Oxford, South Parks Road, Oxford OXI 3FI: UKt ‘School of Biological Sciences, University of Wales, Bram- bell Building, Bangor, Gwynedd LL57 2UK UK

The genetic control theory for schistosomiasis pro- poses that it is possible to reduce the transmission of schistosomes by genetic manipulation of their snail intermediate hosts. It aims to increase parasite-inhibiting genes within natural snail populations by introducing large numbers of artificially selected resistant snails in endemic areas, to the extent, in part, that the local schistosome population cannot adjust co-evolutionarily. This was tested in a laboratory simulation using replicate tanks containing graded proportions of resistant-selected and unselected Biomphalariaglabrata snail lines, exposed to either a high or low Schistosoma mansoni parasite dose. Life history parameters were recorded, indicative of host fitness and parasite virulence, with the aim ofmonitoring each group’s ability to maintain the parasite life-cycle. Our results are discussed in terms of their epidemio- logical and theoretical implications.

248 SHORT PRESENTATIONS

A genetic trade-off ofvirulence and transmission in a snail-schistosome system

C. M. Davies and J. I?. Webster Wellcome Trust Centre for the Epidemiology of Infectious Disease, Depart- ment of Zoology, University of Oxford, South Parks Road, Oxford OX1 3FY, UK

The adaptive trade-off theory for the evolution of parasite virulence requires that virulence be genetically correlated with other fitness characteristics of the para- sites. Many recent evolutionary models rely on a positive correlation between virulence and transmissibility. It is assumed that high parasite burdens are associated with a high probability of transmission and thus increases in parasite fitness, but also with high levels of damage to the host (high virulence). Virulence reduces parasite fitness, by reducing the duration of infection.

Using 2-way artificial selection experiments in a Biomphalarta glabrata-Schistosoma mansoni system, we demonstrated parasite genetic variation for the intensity of infection. We then determined whether the intensity of the infection was genetically correlated with virulence (defined here as a reduction in host survival) and transmission to new hosts. Parasite lines selected for high infection intensities had lower virulence than un- selected control parasite lines. However, parasite lines with high intensities of infection, and low virulence, showed reduced transmission to definitive hosts. Con- versely, parasite lines with low intensity of infection showed increased transmission to definitive hosts. Thus high virulence was associated with high transmission, but this trade-off was not mediated through positive associa- tions of both traits with the numbers of parasites present.

Rearing density of Aedes albopictus and effects on Wolbachia-mediated cytoplasmic incompatibility

T. J. Dutton and S. P. Sinkins Parasite and Vector Biology Division, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 SQA, UK

The mosquito Aedes albopictus is an important vector of dengue and dengue haemorrhagic fever that has extended its range from South Asia to many tropical and some temperate areas. Unidirectional cytoplasmic incompatibility (CI) in crosses between certain Wolba- chia-infected populations (IUMBHAMPATI et al., 1993: Evolution, 47, 673-677) is caused by the presence of 2 strains of Wolbachia in 1 of the populations (SINKINS, S. P. et al., 1995: &oceedings of the Royal Society of London, Series B, 261, 325-330). By PCR analysis and by making crosses between mosquitoes reared under conditions of different larval densities and nutrient levels, this present work aims to investigate any effect of these different conditions on the Wolbachia and therefore on CI. Results indicate that Wolbachia infection, and the penetrance of CI in Ae. albopictus may be reduced under rearing conditions ofhigh larval density and low nutrient. Under conditions of high larval density and high nutri- ent, however, the infection was stable and high pene- trance of CI was found. No decrease in CI with mosquito age occurred, in contrast to results from other species. High levels of CI in most conditions in Ae. albopictus suggest that it may be a favourable system for using Wolbachia as a replacement mechanism to spread useful genes.

[This poster was awardedfirst prize at the meeting.]

Provision of drugs for post-exposure prophylaxis of HIV for medical students on overseas electives

G. F. Franklin and D. Nathwani Infectious Disease Unit, University of Dundee, Dundee DDl 9SY, UK

We assessed the need for, and the most practical way to

provide, post-exposure prophylaxis (PEP) for medical students travelling to areas where this is not readily available. Questionnaires were sent to all 140 students from the University of Dundee returning from their medical elective in 2000, 22 of whom took drugs for PEP with them on elective: 10 1 students (72%) returned questionnaires. Twenty nine (29%) had a significant clinical exposure to potentially infective fluids but only 6 (6%) considered PEP and no-one reported using it. Twelve (12%) students were unaware that PEP was available. Only 15 (15%) might be prepared to pay the full cost of a 5-day starter pack. A high number of students reported significant exposure to potentially infected fluids and this needs to be urgently addressed. There was overwhelming support for provision of PEP and, when it is made available free, students are willing to take it to areas where it is not available.

[This poster was highly commended.]

IgA-responses in saliva and serum versus antigens of Ascaris lumbricoides

E. M. King, L. Drake, J. Webster and E. Michael Wellcome Trust Centre for Epidemiology of Infectious Dis- ease, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3FY, UK

Few detailed studies on the mucosal immune response to human helminthic infections have been performed. Here we have examined the secretory IgA-responses in saliva as well as &A-responses in serum against antigens of adult and larval Ascaris lumbriioides in a high transmis- sion community in Viet Nam. Immunological and para- sitological data from each individual were analysed and compared to give an insight into the role and function of mucosal immune responses as well as the corresponding serum antibody responses in this parasitic infection.

[This poster was awarded second prize at the meeting.]

First record of trypanosomes from the endemic Indian genus ofTriatominae, Linshcosteussp. nov.

J. S. Patterson’, K. Rajen’, D. P. Ambrose’ and M. A. Miles’ ‘Pathogen Molecular Biology and Bio- chemistry Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WCIE 7HT UK; ‘Entomology Re- search Unit, St Xavier’s College, Palayankottai, India

The subfamily Triatominae is composed of 14 genera and some 129 species. The vast majority of species are restricted to the Americas, where several are notorious as vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Only 8 species of Triatoma are known from the Old World and there is 1 genus, Linshcosteus, with 5 species, which is restricted to the Indian sub- continent. Previously little was known of the biology of the genus Linshcosteus. In this study specimens of Linshcosteus were collected from Kalakadu, Tirunelveli District, Tamil Nadu, South India. The bugs were found in a rocky outcrop situated in an area of semi-arid scrub. Hind-gut dissection revealed the presence of trypanoso- matid flagellates, with epimastigotes and small metacyc- lit trypomastigote forms. Preliminary observations of the morphology suggests similarity to T. conorhzlzi, but this requires confirmation. This species of Linshcosteus is morphologically distinct from the 5 known species. Observations of taxonomically important characters re- veal this bug to be different from all other Linschcosteus, and consequently it will be described as a new species. Evidence was found suggesting that the host of these bugs might be rodents, carnivores, bats or possibly reptiles. Future work involving blood-meal analysis by ELISA will clarify the identity of the vertebrate host.

SHORTPRESENTATIONS

Acknowledgements Many thanks to C. Galvlo and J. Jurberg of FIOCRUZ, Brazil

for their help in identifying this new species. We also thank the Sir Halley Stewart Trust, Wellcome Trust and the European Commission for financial support.

[This poster was highly commended.]

Influence of rainfall on pharyngeal carriage of Streptococcus pneumoniae in Tanzania

A, C. Peek, B. M. Charalambous and S. H. Gillespie Department of Medical Microbiology, Royal Free and University College Medical School (Royal Free Campus), Rowland Hill Street, London NW3 2PF, UK

Streptococcus pneumoniae is an important human pathogen, especially among vulnerable groups such as the young, elderly and immunocompromised, causing pneumonia, otitis media, meningitis and bacteraemia. Seasonal variation in pneumococcal carriage rates and pneumonia incidence has been observed (MOGDASY, k. C. et al., 1992: Pediatric Infectious Diseasesjournal, 11, 648-652; BREWSTER. D. R. & GREENWOOD. B. M.. 1993: Annals of Tropiial Paediatriks, 13, 133-126). We have been performing studies of S. pneumoniae carriage and invasive disease. Throat swabs were taken from asymptomatic children and adults and blood cultures from febrile children. S. pneumoniae were isolated and identified by conventional techniques. Rainfall data were obtained from the Tanganyika Planting Company weather stations. Rainfall in iOO0 was sigr&icantly less than in 1999. with onlv 55 mm in March 2000 comnared to 215 mm in Mar& 1999. Samples taken in thk fol- lowing summer months revealed a carriage rate of 20% in 1999, compared to only 7% in the year 2000. Bacter-

aemia rates were also reduced in 2000. The data suggest that changes in rainfall are associated with changes in the rates of carriage and invasive disease.

[This poster was highly commended. ]

The effect ofalphacypermethrin-impregnated nets on sporozoite rates in mosquitoes in Tanzania

Lillian Y. F. Tsang’, Christopher F. Curtis’ and Caroline A. Maxwell”” ‘London School qfHygiene and Tropical Medicine, Keppel Street, London WC1 E 7HT, UK; ‘National Institute for Medical Research Field Station, Box 81, Muheza, Tanga, Tanzania

As part of a study of malaria morbidity and the effec- tiveness oftreated nets in areas that were expected to differ greatly in intensity of malaria transmission, mosquitoes were collected from light traps set in both lowland and highland hamlets in the Muheza district, Tanzania. They were sent to London and by using the ELISA method the CSPisporozoite positivity ;ates and hence the entomolo- gical inoculation rates (EIRs) were determined. The iporozoite rates were sig&ica&ly lowered by the intro- duction of alphacypermethrin-treated nets. The EIRs (per year) foi the-control and treated hamlets were estimated to be 397 and 104 resnectivelv in the lowlands and 16.6 and 5.7 respectively inLthe highlands. Thus the overall impact ofthe nets on EIRforsomeone outside a net was a reduction of 74% in the lowlands and 66% in the highlands. These reduction factors are not as great as in earlier trials in the same area. The EIRin the lowlands was much greater than in the highlands purely because of the larger numbers of mosquitoes in the former; the spor- ozoite rates did not differ significantly.

TRANSACTIONSOFTHEROYALSOCIETYOFTROPICALMEDICINEANDHYGIENE(2001)95,249

1 Book Review 1 I I

Setting up Community Health Programmes-a Practical Manual for Use in Developing Countries (2nd edition). T. Lankester. London and Oxford: Mac- millan Education Ltd, 2000. x+334pp. Price E12.50. ISBN O-333-67933-4.

The premise on which this book is based is that community health care must be grounded in the com- munity and be addressed from the bottom up rather than from the top down. The layout is clear and commences with the principles of community empowerment, part- nership and health awareness which form the basis of community-based health care (CBHC). Three further parts of the book deal with starting a community-based programme, setting up specific programmes and appro- priate management.

Specific programmes include community health clinics, immunization, nutrition, childhood illnesses, maternal health, family planning, tuberculosis, public health and, slightly out of place at the end of the book, AIDS care.

Each chapter begins with an introductory plan and consists of 2 main sections: ‘What we need to know’ and ‘What we need to do’. Key points are boxed to focus our attention. Line drawings and cartoons appropriately illustrate key situations. The chapters conclude with a summary and a list of further reading and learning materials. Finally 7 appendices gather together ex- tremely useful information on suppliers of necessary equipment, essential drugs, journals and newsletters with addresses of resource and information centres and a summary of programme records which have been

suggested throughout the text. Finally there is a compre- hensive index and a list of abbreviations.

The book is invaluable for anyone involved in primary health care including doctors, nursing and paramedical professionals and health care workers at all levels. It is full of detailed strategies and remedies and how to put them into practice and evaluate their effectiveness. These clearly derive from the experiences not only of the author but from many sources with hands-on exposure and familiarity with grassroot community care and concerns.

The author makes little mention of WHO’s Integrated Management of Childhood Illnesses. I felt more empha- sis could have been put upon participation of the community in the curative care of illness which can so powerfully influence its further prevention in such examples as the rehabilitation of the malnourished child, the use of oral rehydration solution in dehydration, treatment compliance in tuberculosis, the treatment of sexuallv transmitted disease in reducing HIV transmis- sion, eic. One or two issues could ha&been expanded with benefit, such as contact tracing of childhood and ‘open’ tuberculosis, and the prevention of HIV transmis- sion. Accidents including aspiration of foreign bodies in childhood were omitted and a statement that malnour- ished children under the age of 2 years have smaller brains than normal children needs a lot of qualifying and, as it stands, could lead to unnecessary concern.

These quibbles do not detract in anyway from a book of extreme value to those who are faced with the initiation, development, management and sustaining of community health care programmes in developing countries.

Paget Stanfield Consultant in maternal and child health in developing countries Inverlussa, Bridgend, Callandar Perthshire FK17 8AG, UK