Study on the sequential tsetse-transmitted Trypanosoma congolense, T. brucei brucei and T. vivax infections to African buffalo, eland, waterbuck, N'Dama and Boran cattle

Susceptibility of African buffalo, eland, waterbuck, N'Dama and Boran cattle to sequential Glossina morsitans centralis-transmitted infections of Trypanosoma congolense, T. brucei brucei and T. vivax was compared, and their possible role as reservoirs of these parasites for G. moristans centralis, G. pallidipes, G. austeni, G. brevipalpis and G. longipennis determined. The buffalo, eland, waterbuck and N'Dama controlled T. congolense parasitaemias and were able to prevent anaemia. By contrast, one Boran became severely anaemic whilst the other controlled parasitaemia and anaemia. When the above five species of Bovidae were rechallenged with T. brucei brucei they showed persistent parasitaemias but did not develop anaemia. The buffalo died of other causes. When the remaining four bovids were rechallenged with T. vivax they became infected with mixed T. vivax/T. b. brucei parasites. Eland, waterbuck and N'Dama controlled parasitaemias and anaemia whereas the Boran became anaemic. Cyclical development of T. congolense occurred in G. moristans centralis when fed on the bovid hosts, with buffalo being infective for tsetse flies for a much longer period. There was no relationship between the levels of T. congolense parasitaemia in the bovid hosts and the resultant infection rates in tsetse flies. Glossina m. centralis was more susceptible than G. pallidipes to T. brucei brucei whilst G. austeni the least; G. brevipalpis and G. longipennis were refractory to the mature infection. Again there was no relationship between T. brucei brucei parasitaemia levels in the hosts and infection rates in the flies. Glossina m. centralis and G. pallidipes showed mixed T. brucei brucei/T. vivax infections whilst G. austeni, G. brevipalpis and G. longipennis became infected with T. vivax alone. Tsetse flies showed higher T. vivax infection rates when fed on the hosts with high parasitaemias than thosewith low parasitaemias. Thus trypanotolerant African buffalo, eland, waterbuck, N'Dama as well as some trypanosusceptible Boran cattle can serve as reservoirs of single or mixed trypanosome infections for tsetse flies. This study has also shown that the Ag-ELISA on the sera from the five bovid hosts had low sensitivity and species-specificity. Examinations of thin wet blood films and buffy coats with a phase-contrast microscope were not sensitive enough to detect the parasites on all occasions. Xenodiagnosis using mice for T. brucei brucei and T. congolense infections, and tsetse flies for all the three trypanosome species were most sensitive for the detection of trypanosome infections in the bovid hosts.     

Developmental plasticity of ascending spinal axons studies using the North American opossum, Didelphis virginiana

The polymerase chain reaction was used to characterize the trypanosomes infecting Glossina morsitans submorsitans and G. tachinoides in the game ranch of Nazinga, Burkina Faso, situated near an agropastoral zone. Dissection of 435 tsetse flies, and PCR analysis of 166 infected flies were conducted to assess the epidemiological situation. Trypanosomes of the Nannomonas subgenus were the most abundant in the two tsetse species (80.4% and 73.7% of identified infections in G. m. submorsitans and G. tachinoides respectively). T. vivax and T. brucei infection rates were comparable between the two tsetse species. Mature infection pattern identified by PCR differed from overall infections, mainly because T. simiae infections did not mature, whereas T. vivax represented the predominant taxon. Parasitological and PCR results showed some discrepancies; possibly some typical Duttonella strains could not be recognized by the sets of primers used. The technologies used in this work helped to determine the high trypanosomosis risk in this area.     

Unusual presentation of a meniscal tear: a case report

Ten taxa of Stomoxyinae were tested for their ability to transmit Trypanosoma brucei, T. vivax, T. evansi and T. congolense to mice within 3 min of interrupted feeding on highly parasitaemic blood. T. brucei was the easiest parasite to transmit with an 11.5% success rate, followed by T. vivax at 3.4%, and T. evansi at 0.9%. T. congolense was not transmitted in 129 attempts. Stomoxys niger sspp. and four unstudied species (S. varipes, S. taeniatus, S. pallidus, Haematobosca squalida) were capable of transmitting trypanosomes mechanically.     

Sensitivity and specificity of antigen-capture ELISAs for diagnosis of Trypanosoma congolense and Trypanosoma vivax infections in cattle

Sensitivity and specificity of the FAO/IAEA antigen-ELISA kits for diagnosis of bovine trypanosomosis were investigated using sera from experimental cattle infected by tsetse challenge with cloned populations of Trypanosoma congolense (three populations) or T. vivax (one population). The kits are based on monoclonal antibodies that recognise internal antigens of tsetse-transmitted trypanosomes. Ten cattle were infected with each trypanosome population for at least 60 days, and in combination with uninfected cohorts (n = 16) were used in a double-blind study design. Sensitivity and specificity of the tests depended on the choice of positive-negative thresholds expressed as percent positivity with respect to the median OD of four replicates of the strong positive reference serum provided with the kit. In general, while overall specificities were high, sensitivities of the antigen-ELISAs were poor. For example, at a cut-off of 5% positivity, the sensitivities of the antigen-ELISAs were 11% for samples (n = 1162) from T. congolense infected cattle (n = 30), and 24% for samples (n = 283) from T. vivax infected cattle (n = 10). The corresponding specificity values were 95% and 79%, respectively. At a cut-off of 2.5% positivity sensitivity for T. congolense was 25%, and for T. vivax 35%; corresponding specificity values were 85% and 63% respectively. There were no values of the positive-negative threshold at which both sensitivity and specificity were satisfactory. Restricting the analyses to samples taken more than 2 weeks after tsetse challenge did little to improve sensitivity estimates. Trypanosome species specificities of the antigen-ELISAs were also poor. Sensitivity and species specificity of the antigen-ELISA for Trypanosoma brucei infections were not investigated. In contrast to the antigen-ELISA, the sensitivity of the buffy-coat technique when applied to the same experimental animals was fairly high at 67% for T. congolense infections and 60% for T. vivax infections. For samples taken more than 2 weeks after tsetse challenge, high sensitivity estimates of 96% for T. congolense and 76% for T. vivax infections were obtained.     

New aspects of malaria imported from Ethiopia

We describe a high incidence of Plasmodium vivax malaria among travelers returning from Ethiopia, who all took the recommended prophylaxis. Three groups of 7-11 nonimmune travelers received mefloquine (250 mg weekly), beginning 1-2 weeks prior to departure and continuing for 4 weeks after their return. A fourth group mistakenly took inadequate prophylaxis and is presented for comparison. Vivax malaria occurred at a rate of up to 50% in the first three groups; nearly all patients became ill 3 months after exposure. In the fourth group, primary attacks of both falciparum and vivax malaria occurred within 1 month of return, at an incidence of 50%. The use of mefloquine prevented Plasmodium falciparum infection, but a very high rate of relapses of P. vivax infection occurred. The complexity of prophylaxis for malaria in an area with a high rate of both P. falciparum and P. vivax infections and the urgent need for effective causal prophylaxis are discussed.     

Malaria surveillance -- United States, 1994

PROBLEM/CONDITION: Malaria is caused by infection with one of four species of Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, and P. malariae ), which are transmitted by the bite of an infective female Anopheles sp. mosquito. Most malarial infections in the United States occur in persons who have traveled to areas (i.e., other countries) in which disease transmission is ongoing. However, cases are transmitted occasionally through exposure to infected blood products, by congenital transmission, or by local mosquitoborne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to adapt prevention recommendations. REPORTING PERIOD COVERED: Cases with onset of symptoms during 1994. DESCRIPTION OF SYSTEM: Malaria cases confirmed by blood smear are reported to local and/or state health departments by health-care providers and/or laboratories. Case investigations are conducted by local and/or state health departments, and the reports are transmitted to CDC through the National Malaria Surveillance System (NMSS), which was the source of data for this report. Numbers of cases reported through NMSS may differ from those reported through other passive surveillance systems because of differences in the collection and transmission of data. RESULTS: CDC received reports of 1,014 cases of malaria with onset of symptoms during 1994 among persons in the United States or one of its territories. This number represented a 20% decrease from the 1,275 cases reported for 1993. P. vivax, P. falciparum, P. malariae, and P. ovale accounted for 44%, 44%, 4%, and 3% of cases, respectively. More than one species was present in five persons (<1% of the total number of patients). The infecting species was not determined in 50 (5%) cases. The number of reported malaria cases in U.S. military personnel decreased by 86% (i.e., from 278 cases in 1993 to 38 cases in 1994). Of the U.S. civilians who acquired malaria during travel to foreign countries, 18% had followed a chemoprophylactic drug regimen recommended by CDC for the area to which they had traveled. Five persons became infected while in the United States; the infection was transmitted to two of these persons through transfusion of infected blood products. The remaining three cases, which occurred in Houston, Texas, were probably locally acquired mosquitoborne infections. Four deaths were attributed to malaria. INTERPRETATION: The 20% decrease in the number of malaria cases from 1993 to 1994 resulted primarily from an 86% decrease in cases among U.S. military personnel after withdrawal from Somalia. Because most malaria cases acquired in Somalia during 1993 resulted from infection with P. vivax, there was a proportionately greater decrease during 1994 in the number of cases caused by P. vivax relative to those caused by P. falciparum. ACTIONS TAKEN: Additional information was obtained concerning the four fatal cases and the five cases acquired in the United States. Malaria prevention guidelines were updated and distributed to health-care providers. Persons traveling to a geographic area in which malaria is endemic should take the recommended chemoprophylactic regimen and should use protective measures to prevent mosquito bites. Persons who have a fever or influenza-like illness after returning from a malarious area should seek medical care; medical evaluation should include a blood smear examination for malaria. Malarial infections can be fatal if not promptly diagnosed and treated. Recommendations concerning prevention and treatment of malaria can be obtained from CDC.     

Incidence of Toxoplasma and Toxocara antibodies among out-patients in the Ophthalmic Research Institute, Egypt

Infection by Toxoplasma gondii and Toxocara canis is getting much important nowadays. Both are soil transmitted infections. The present study was planned to detect the incidence of T. gondii and T. canis antibodies among 100 patients attending the outpatient clinics in Research Institutes of Ophthalmology (RIO), whose urine and stool were free from other parasitic stages. Patients were classified into two groups, group I; (70 ocular cases) and group II, (30 non-occular cases). Control group (group III); 30 healthy persons. Sera from all individuals were subjected to IFAT and IHAT to detect Toxoplasma antibodies and IFAT to detect Toxocara antibodies. By using IFAT for Toxoplasma revealed, 25% as a total incidence, 21.4% in group I, 33.3% in group II and 6.6% in group III. While IHAT revealed 51% as a total incidence, 51.4% in group I, 50% in group II and 23.3% in group III. Among group I, retinochoroiditis cases showed the highest incidence and titre. While hydrocephalic cases showed highest incidence and titre in group II. T. canis antibodies revealed 23% as a total incidence, 14.3% in group I, 43.3% in group II and 5% in group III. Cases presented with retinal detachment showed the highest incidence and titre in group I while in group II hepatomegalic cases gave the highest incidence and titre. Concomitant infection of both Toxoplasma and Toxocara was detected in 8% of positive cases.     

Psychiatric comorbidity in patients with burning mouth syndrome

This paper reports the efficacy results of the randomized, placebo-controlled, field trial of SPf66 malaria vaccine in Costa Marques, Rondonia, Brazil. This region is characterized by the seasonal distribution of Plasmodium falciparum and P. vivax infections, and the recent occupation by migrants from nonendemic areas. A total of 800 individuals of both sexes, ranging in age from seven to 60 years, were included in the study. Of the initial cohort, 572 participants completed the vaccination schedule. Clinical and parasitologic evaluations were obtained by active and passive searches on a periodic basis. The overall protective efficacy against P. falciparum infections was -1.6% (-32.9% to 22.4%), and 14.1% (-17.0% to 36.9%) for the first episode. The overall protective efficacy for P. vivax infections was -19.7% (-44.8% to 1.03%), and -10.8% (-41.1% to 12.8%) for the first episode. No statistical evidence of an overall significant protective effect of SPf66 malaria vaccine against P. falciparum and P. vivax malaria was obtained in this trial.     

Herd immunity to filarial infection is a function of vector biting rate

Despite the existence of an impressive body of work on human immune responses against filarial infections, the occurrence of a protective response to infection remains unclear. Here, we use a combined modelling and comparative data analysis framework to address this issue for human infections with the filarial parasite, Wuchereria bancrofti. By analogy with previous work, the analysis involves the comparison of observed field patterns of infection with epidemiological patterns predicted by a mathematical model of parasite immunity. Unlike most other human helminths, which are transmitted by ingestion or dermal penetration, exposure to infection with lymphatic filariasis can be measured explicitly in terms of vector mosquito biting rates, thereby also allowing, probably for the first time, examination of the suggested role of exposure in generating herd immunity to macroparasites. Observed field patterns in this study were derived from 19 different published studies, which gave parallel estimates of community exposure rates and the corresponding age--prevalence patterns of infection, while predictions of the epidemiological impact of herd immunity were obtained using a catalytic model framework. The results provide the first conclusive evidence to date that variations in the observed age--prevalence patterns of infection in filariasis can be effectively explained by the occurrence of an exposure-driven acquisition of herd immunity. We discuss this result in terms of implications for the new World Health Organization-led initiative for the global control of this parasitic disease.     

Adenosine-induced transient cardiac asystole enhances precise deployment of stent-grafts in the thoracic or abdominal aorta

BACKGROUND: Anaphylaxis to the bite of Diptera and specifically the bite of the Tabanidae family (horsefly) have been sparsely documented. The coexistent hypersensitivity to both the order Diptera and Hymenoptera has not been documented. METHODS: We present a patient who experienced anaphylaxis to both insect species. Venom skin testing and RAST revealed sensitivity to several members of the Hymenoptera order. Prick, intradermal and RAST with whole body extracts of Tabanidae species is also documented in this patient. Twenty patients who are sensitive to Hymenoptera and have been bitten by horseflies but have had no reaction to the horsefly bite were used as controls. RESULTS: An anaphylactic reaction to horsefly bite has been documented in a 56-year-old white male. This patient also demonstrated evidence of anaphylactic reaction to Hymenoptera envenomation. In controls consisting of 20 patients with Hymenoptera sensitivity, there was no clinical history of reaction to horsefly bite despite the presence of positive prick and/or positive intradermal tests and/or positive RAST to mixed Tabanidae species extract. CONCLUSIONS: Skin testing to horsefly by prick and/or intradermal testing using whole body insect extract is not useful in making a diagnosis of Tabanidae hypersensitivity. RAST using Tabanidae species as antigen is similarly useless in making a diagnosis of Tabanidae hypersensitivity. In vivo and in vitro diagnosis of horsefly hypersensitivity may be achieved when the salivary gland antigen of the horsefly becomes available.     

Plasmodium vivax infections in chimpanzees for sporozoite challenge studies in monkeys

The development and testing of vaccines directed against Plasmodium vivax has relied on Saimiri and Aotus monkeys as the animal test system and on chimpanzees to provide infective gametocytes to produce sporozoites for monkey challenge studies and vaccine development. One sporozoite-induced and 29 blood-induced infections with the Salvador I strain of P. vivax were studied in splenectomized chimpanzees. Eighteen primary infections with P. vivax resulted in maximum parasite counts ranging from 1,519 to 81,810/ microliters (median 29,100/microliters). Twelve infections induced in animals previously infected with the homologous or heterologous strains of P. vivax had maximum parasite counts ranging from 155 to 14,136/microliters (median 1,736/microliters). A total of 202 of 237 lots containing a total of 293,175 Anopheles freeborni, An. stephensi, An. gambiae, An. dirus, An. quadrimaculatus, and An. maculatus mosquitoes were infected by membrane feeding on gametocytes from chimpanzees. Despite lower levels of parasitemia during secondary (reinfection) parasitemia, 66 of 70 lots of mosquitoes (94.3%) were infected. Based on the mean number of oocysts per positive mosquito gut, An. freeborni was more heavily infected than An. stephensi; An. stephensi was more heavily infected than An. gambiae; there was no significant difference between An. stephensi and An. dirus. Sporozoites from An. stephensi, An. gambiae, An. dirus, and An. freeborni infected with the Salvador I strain of P. vivax produced in chimpanzees were used to infect 193 Saimiri and six Aotus monkeys as well as one chimpanzee.     

Adolescent sexuality: Part 4. The practitioner''s role

As no systematic study has been done to get an accurate estimate of the incidence of return to oestrus after first insemination in sows in the Netherlands, the objectives of this investigation were: 1) to obtain an estimate of the incidence of return to oestrus after insemination at the herd level; 2) to investigate the association between incidence of return to oestrus after first insemination and reproduction characteristics in order to get an impression of the economic importance of reproductive failure. These objectives were investigated by using the reproduction results of 240 swine breeding herds in the Southern Netherlands in 1987. This information was obtained from CBK plus computerized herd management records. The average incidence rate of return to oestrus after first insemination at a herd level was 16.9 per 100 first inseminations. The occurrence of return to oestrus after first insemination was distinctly higher in the insemination months July and August compared to the rest of the year. An increased incidence, with 10 returns per 100 first inseminations corrected for confounders in a multiple linear regression model, was associated with a decrease of approximately 0.3 live born piglets/sow/year. A prospective longitudinal study was started in 1988 and 1989 in 37 sow herds. Individual sows were monitored from weaning to first insemination, to the occurrence of return to oestrus, or not, after first insemination, and to farrowing. The investigation focused in particular on the relationship between return to oestrus after first insemination and seroconversion against porcine parvovirus (PPV) and Leptospira interrogans serovar bratislava (L. bratislava).(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidemiological features of severe paediatric malaria in north western Ethiopia

Malaria remains a major public health challenge in sub-Saharan Africa, yet our knowledge of the epidemiology of malaria in terms of patterns of mortality and morbidity is limited. To examine the clinical and epidemiological presentation of severe life-threatening malaria in Humera, north western Ethiopia studies were conducted among the childhood population in the community, those presenting to out-patient facilities and those admitted to the district hospital. The overall P. falciparum parasite rate among children aged 0-9 years resident within the area was only 12% confirming the low level of endemicity in this area. P. vivax infections were present in 5% of children. Between July 1993 and June 1994 peak out-patient presentation with Plasmodium falciparum coincided with the rains with over 50% of cases occurring between August and October whilst P. vivax infections were predominant during the hot, dry months. Malaria was an important cause of paediatric admission to the local district hospital with an estimated 4.7% of the at-risk childhood community warranting intensive clinical management each year. Case fatality rates were high and the clinical spectrum of severe disease indicated a preponderance of cerebral malaria cases. In addition, respiratory distress was a feature in 12% of the malaria admissions. The suggestion that the coexistence of Plasmodium falciparum and Plasmodium vivax may serve to reduce the severe clinical consequences of P. falciparum malaria is not supported by these observations.     

Ovine trypanosomosis: a seroepidemiological survey in coastal Guyana

The objective of this study was to determine the seroprevalence rates of Trypanosoma vivax and Trypanosoma evansi in sheep in coastal Guyana. Blood samples were taken from a systematic random sample of one hundred and ninety-three (193) sheep on twenty-two (22) farms in Region 5, Mahaica/Berbice, a coastal area of Guyana. Age, breed, sex, and farm of origin were recorded for all sampled sheep. One hundred and seventy-six (176) serum samples were submitted for Indirect Fluorescent Antibody (IFA) testing for T. vivax and T. evansi. Fluorescence was graded as 0 (negative), 1+(very weak), 2+(weak), 3+(strong) or 4+(very strong), measured at 1:160 dilution of serum. Samples were considered to be sero-positive if any fluorescence was observed. Indirect Fluorescent Antibody results were received for one hundred and sixty-one (161) samples. One hundred and three (64%) sera were sero-positive for Trypanosoma sp. Of these, 38 (23.6%) sera were positive to T. evansi only, 11 (6.8%) were positive to T. vivax only and 54 (33.5%) were positive for both. As cross reactions occur between T. vivax and T. evansi, it was difficult to determine the true species of exposure for the sera which tested positive to both species. The overall sero-prevalence rate of 64% suggests that trypanosomosis is endemic in sheep in coastal Guyana. This was the first serological evidence of T. evansi in Guyana. Although T. vivax is believed to be pathogenic in sheep, the clinical significance of T. evansi remains unknown. The vector of both species of trypanosomes in sheep on the north coast of South America also is not known.     

Cloning and analysis of the human complement factor H gene promoter

The compound WR 238605 is a primaquine analog being developed by the U.S. Army as an antimalarial drug. Currently, there is no established treatment for Plasmodium vivax parasitemias that are not cured by chloroquine. This study tested WR 238605, chloroquine, and their combinations against a chloroquine-resistant strain of P. vivax (AMRU 1) in Aotus monkeys. A total dose of 3 mg/kg of WR 238605 given at a dosage of 1 mg/kg/day for three days cleared patent parasites in all eight monkeys but recrudescence of parasitemia occurred 15-25 days after initiation of treatment. A total dose of 9 mg/kg of WR 238605 over a three-day period cured all three monkeys of their infections. A total dose of 30 mg/kg of chloroquine did not clear patent infections in three monkeys, whereas a total dose of 60 mg/kg generally (two of three) cleared patent parasitemia but did not cure. Whereas total doses of 30 mg/kg of chloroquine or 3 mg/kg of WR 238605 given alone failed to cure, both drugs given in combination at these dosages cured two of three infections. These results indicate that WR 238605 may be an alternative treatment for chloroquine-resistant vivax malaria.     

Dynamic stochastic simulation as a tool for studying bovine virus diarrhoea virus infections at the herd level

Infectious diseases, such as bovine virus diarrhoea (BVD) virus infections in cattle, are often studied by Markov chain models. However, it is difficult to simulate dynamic interactions between production of a reproductive herd and the disease by this type of model. As an alternative, a dynamic stochastic model simulating the herd production was suggested. A dynamic stochastic model simulating the effect of BVD virus infection in a dairy cattle herd was used to exemplify how this type of model could be applied in research. The simulation example demonstrated that the effect of a BVD virus infection depended on the characteristics of the individual herd.     

School-based mental health services in the United States: history, current models and needs

The prevalence of ruminant trypanosomosis and tsetse flies was investigated in Katsina-Ala Local Government Area--a sleeping sickness endemic area--between the valleys of River Benue, Katsina-Ala and Donga in Central Nigeria. Analysis of three hundred and twenty blood samples showed that among semi-nomadic animals, about one cattle (21.3%; 0.213, confidence interval C1 +/- 0.06) and two sheep (38.0%; 0.380, C1 +/- 0.10) out of five carried mature trypanosome infections. Significantly lower (P < 0.05) values (12.5%; 0.125, C1 +/- 0.08) were recorded among peri-domestic West African Cross Red Sokoto (WAD x RS) goats. Trypanosoma vivax was the most prevalent species encountered; it was diagnosed in 10.3% of the ruminant population and responsible for 42.8% of the infections in all animals. Corresponding figures for T. congolense were 5.9% and 24.6%, respectively. T. brucei infections were low in cattle (1.8%) and absent in goats. Males and young stock had lower infection but the difference was not significant (P > 0.05) except between the ages in cattle. Glossina tachinoides was the only tsetse species encountered and responded to acetone odour attractant in biconical traps.     

Cloning and characterization of the human and Caenorhabditis elegans homologs of the Saccharomyces cerevisiae MSH5 gene

Genetic variation among malaria parasites has important consequences with regard to drug resistance, pathogenicity, immunity, transmission, and speciation. In this regard, malaria parasites have been shown to display a high degree of inter- and intra-species genetic divergence. The nuclear genomes of Plasmodium falciparum, Plasmodium yoelii, and Plasmodium gallinaceum are vastly divergent yet share a similar codon usage and total A/T content of approximately 82%. This is in contrast to other primate-specific species including P. vivax which have an A/T content of approximately 67%. To assess the effects of this evolutionary divergence on the conservation of gene content, organization, and codon usage in the mitochondrial DNA (mtDNA) of malaria parasites, we have cloned and sequenced the mitochondrial genome of Plasmodium vivax, and compared it with the mtDNAs of P. falciparum, P. yoelii, and P. gallinaceum. The P. vivax mitochondrial genome was found to be 5990 base pairs in length, and displayed a gene organization identical to that of P. falciparum, P. yoelii, and P. gallinaceum. Furthermore, there was a remarkable 90% conservation of sequence identity between the mitochondrial genomes of all four species. As an example of intra-species conservation, comparison of mtDNAs from two independently cloned P. falciparum isolates, Malay Camp and C10, revealed only a single nucleotide substitution. A/T content of the P. vivax mitochondrial genome was found to be identical to other species of Plasmodium, hence, we have postulated that the mitochondrial genomes of malaria parasites were refractory to the evolutionary shifts in nucleotide content seen among the nuclear genomes of malaria parasites. Among different Plasmodium species, the second position of mitochondrial codons were found to be the least prone to substitutions and displayed a significant bias in pyrimidines. These aspects of mitochondrial codon usage were distinct from the nuclear genome and may reflect functional aspects of decoding by the mitochondrial translational system.     

IgE, IgA, and IgG responses to common yeasts in atopic patients

To assess the incidence of HIV infection and risk factors associated with HIV seroconversion among patients attending clinics for sexually transmitted diseases (STD), medical record reviews were conducted in 12 clinics in 7 U.S. cities. The records of all patients who initially tested negative for HIV from 1991 through 1996 and who received at least one additional HIV test during the study period were reviewed. In each of 7 cities, 5 to 112 patients seroconverted. Of the 286 seroconverters identified in total, 53% (152 of 286) were heterosexual men and 28% (81 of 286) were women. HIV incidence rates among men who have sex with men (MSM) ranged by city from 0.81 to 7.0 new infections/100 person-years. Rates among heterosexual men and women ranged from 0.018 to 1.2 infections/100 person-years. Multivariate analyses showed that drug use was associated with HIV seroconversion only among heterosexuals. Most new HIV infections in these clinics are being transmitted heterosexually and are associated with drug use. Nevertheless, MSM, particularly young MSM, are at greatest risk for HIV in this population: 1 of 47 seroconvert/year. The effective use of targeted prevention efforts depends upon the continued ability to monitor the incidence of HIV infection.