Evidence for the occurrence of Schistosoma intercalatum at Albert Nile in northern Uganda.

During a field investigation in Rhino Camp at Albert Nile in northern Uganda, 77.8% of 636 persons excreted Schistosoma mansoni ova that were detected by the Kato-Katz method. Six patients, 8-17 years of age, had terminally spined schistosome eggs in their stools. These findings were confirmed when preserved specimens were examined at the Institute of Medical Parasitology in Bonn using a concentration technique. The mean +/- SD length of 36 terminally spined eggs was 156 +/- 6 microns and the mean +/- SD width was 59 +/- 3.6 microns. Urine filtration in the study patients revealed no schistosome eggs in the urine. It is concluded that these findings provide evidence for the occurrence of S. intercalatum at Albert Nile in northern Uganda.

Toxoplasma gondii antibodies in pregnant women and their newborns in Dar es Salaam, Tanzania.

The sera of 849 Tanzanian pregnant women were tested at delivery for Toxoplasma gondii antibodies with the Sabin-Feldman dye test (DT) and an immunosorbent agglutination assay. A total of 296 (35%) of these women had DT titers greater than 1:4. The percentage of women with dye test titers greater than 1:4 was 34-37% regardless of the individual ages. The rate of positivity for human immunodeficiency virus 1/2 (HIV-1/2) using Western blotting was 11.5%. There was no relationship between prevalence of a positive DT result and HIV infection nor between the intensity of the DT result and HIV infection. Sixty-four parturients had a DT titer of 1:1,000 or more. From 57 newborns of these mothers, cord sera were available and were screened by the DT and the immunosorbent agglutination assay. Seven of these were found to be positive for IgM and/or IgA antibodies. It was concluded that the rate of serologic evidence for prenatal Toxoplasma infection in cord blood samples in the present study of Tanzanian pregnant women was approximately 0.8%.

Acrosomal proteinase inhibitors in rhesus monkey (Macaca mulatta) oviduct fluid.

PIP: Acrosomal proteinase inhibitors were found in rhesus monkey fallopian tubes. Spermatozoa contain a proteolytic enzyme in their acrosomal heads and which would be adversely affected by the presence of acrosomal proteinase inhibitors. The inhibitor concentration was high before ovulation, decreased to low levels around the time of ovulation, and rose to high levels again within 1-3 days after ovulation. Alpha-1-antitrypsin, alpha-2-macroglobulin and alpha-1-antichymotrypsin all followed this high-low-high pattern. Alpha-1-antitrypsin in human cervical mucus is found to follow a similar waxing and waning according to progesterone secretion.^ieng

Influence of the oviduct on sperm capacitation in the rabbit.

PIP: In an effort to evaluate the influence of the oviduct on sperm capacitation, in vitro fertilization of freshly-ovulated rabbit ova was used to assay the fertilizing ability of spermatozoa. New Zealand white rabbits were used. 9 1/2 hours after injection of human chorionic gonadotrophin half the animals had fimbriae of both tubes resected; 2 hours later, the ovaries were excised and the ova in cumulus removed from the surface of the ovaries. Half the animals serving as donors of uterine spermatozoa had their oviducts removed; half were intact. Both had spermatozoa recovered from their uteri 6-48 hours after mating. Study technique is detailed. Studies of 617 ova showed best fertilization rates when spermatozoa had remained in the uteri 16-18 hours. Spermatozoa recovered from capacitators without oviducts produced similar cleavage rates as those with intact oviducts. Results indicate that spermatozoa can be capacitated in the uterus of rabbits without oviducts but it is possible that part of the capacitation normally takes place in the oviducts. Others have shown capacitation takes longer by several hours with the uterotubal junction ligated than when this junction is patent. Ova were fertilized by spermatozoa recovered from the uterus after 8 hours but not by those recovered after 6 hours. In the present experiment spermatozoa recovered from the uterus 36 hours postcoitus were still able to fertilize ova.^ieng

Postoperative intraperitoneal adhesions: a double-blind assessment of their prevention in the monkey.

PIP: The effect of combined antihistamine and corticosteroid therapy and the effect of dextran on recurrent intraperitoneal adhesion formation were evaluated in 43 monkeys, all of which had been previously used for reproductive tract studies, and, hence, were suffering from adhesion formation to some degree. In a double-blind manner, the monkeys were randomly divided into 3 experimental groups. 1 group received saline injections before and after lysis surgery followed by introduction of saline solution in the peritoneum during surgery. Group 2 was treated with saline injections, as Group 1, except that dextran solution was introduced into the peritoneal cavity. In Group 3, a combined dexamethasone/promethazine therapy was administered before, during, and after surgery. In all of these monkeys, the degree of adhesion reformation after adhesion lysis surgery was essentially the same in all 3 groups. Rather, careful surgical technique was vastly more important than use of corticosteroids or antihistamines as prophylactic measures.^ieng

A histological study of skin reactions of baboons to Schistosoma mansoni schistosomula.

A histological study was undertaken of the cellular reaction in the skin of baboons challenged with cercariae of Schistosoma mansoni. Control animals with no previous schistosome infection were compared with baboons that had infections of varying duration. In animals infected for 10 weeks no striking inflammatory reaction was seen, the histological picture being very similar to that of the control animals. After 8 months of infection the hosts developed a strong cellular response to the invading schistosomula. The predominant cells in these reactions were eosinophil leucocytes which sometimes closely adhered to degenerating schistosomula. However, some unaffected schistosomula were found close to these intense cellular reactions, suggesting that schistosomula possess varying ability to resist the host's immunological attack.

A comparison of phase contrast microscopy and an immunofluorescence test for the detection of Giardia spp. in faecal specimens from cattle and wild rodents.

As part of a study on the presence of Giardia cysts in water, a commercial direct immunofluorescence (DIF) test for the cysts was evaluated and compared to phase contrast microscopy. Forty faecal samples were collected from cattle; 31 contained Giardia. All 31 samples were positive by DIF whereas only 17 were detected by microscopy. The detected Giardia cysts were identified as belonging to the G. duodenalis group. 216 faecal samples were collected from wild rodents (Apodemus flavicollis, A. sylvaticus and Clethrionomys glareolus); 103 contained Giardia. Cysts were detected in 97 samples by DIF and in 57 by microscopy; 51 samples were positive by both methods. Nineteen rodents harboured cysts which morphologically resembled G. duodenalis. Specific identification was possible only by phase contrast microscopy, but the results suggested that DIF was superior for the detection of Giardia cysts in faeces of the animals tested.

Observations on possible immunity to reinfection among Kenyan schoolchildren after treatment for Schistosoma mansoni.

In February 1977, 306 out of 409 six- to 16-year-old Kenyan schoolchildren were found to be infected with Schistosoma mansoni. Prevalence and intensity were directly related to age and indirectly to the distance between the child's home and the transmission site, but were not related to the child's sex. Most children were treated with hycanthone in July 1977. Pretreatment blood samples were taken from 100 study children for eosinophil counts and measurements of cytotoxic anti-schistosomular antibody levels. Blood and faecal samples were re-examined five times between November 1977 and July 1979. Whole school resurveys in July 1978 and 1979 confirmed the continuation of transmission after chemotherapy. 'Reinfection' rates in the study children, incorporating both failed treatment and true reinfections, were significantly reduced in children, with both detectable antibody and eosinophil counts above 400/mm3, compared with children with neither. Children with either detectable antibodies or high eosinophil counts (mainly the latter) had intermediate reinfection rates. Neither sex, age nor pretreatment intensities influenced reinfection rates, but location of dwelling did: children from distant homes had lower rates. However, the effects of residence and 'protection' were not directly linked. The implication of these results, namely that infection can confer immune protection to reinfection after treatment, is being explored in further studies.

Infestation of rodents with larval Ixodes ricinus (Acari: Ixodidae) is an important factor in the transmission cycle of Borrelia burgdorferi s.l. in German woodlands.

The ecology of Borrelia burgdorferi Johnson et al. s.l. was investigated from 1987 to 1993 in a preserved woodland in western Germany near Bonn. In selected biotopes, host-seeking Ixodes ricinus L. were regularly collected by blanket dragging in 1987, 1988, and 1989 and screened for infection with B. burgdorferi. Rodents were trapped monthly between April and October in 1988, 1990, 1991, and in the winter of 1992-1993, examined for antibodies to B. burgdorferi s.l., and inspected for feeding ticks. Ticks collected from rodents were screened for spirochete infection. High numbers of host-seeking nymphs were consistently collected within a biotope characterized by humid and acid soils. The mean number of ticks was significantly lower in biotopes with permeable soils. All small mammals captured belonged to the species Apodemus flavicollis Melchior, A. sylvaticus L., and Clethrionomys glareolus Schreber. Of 11,680 ticks obtained from rodents, 11,674 were I. ricinus, with 97.9% of the ticks being larvae, 2.0% nymphs, and 0.1% females. Mean numbers of feeding ticks ranged from 3.4 to 117 larvae per rodent and from 0.0 to 0.64 nymph per rodent, respectively. High levels of larval infestation on rodents were recorded in the same biotope where high numbers of host-seeking nymphs were present. Members of the genus Apodemus were more heavily infested with I. ricinus larvae than C. glareolus. The mean infection prevalence in host-seeking ticks was found to be 1% for larvae, 5% for nymphs, and 10-20% for adults. The infection prevalence in host-seeking nymphs ranged from 1.1 to 15.4% according to the particular biotope. The values for specific infectivity for the Apodemus populations were positively correlated with the mean larval infestation, but not with nymphal infestation. The respective estimates for C. glareolus were much higher than those for Apodemus spp. in biotopes with low tick densities. However, specific infectivity of C. glareolus was substantially reduced at sites with high tick abundances. In biotopes with high numbers of infected I. ricinus, significantly more rodents were found to have antibodies to B. burgdorferi than in biotopes with low abundances of ticks. The data show that C. glareolus plays a different role as reservoir host species compared with the 2 Apodemus species. This and previous studies suggest that the degree of infestation with larval I. ricinus differentially modulates infectivity of host species for ticks. We conclude that immune processes in natural reservoir hosts induced by B. burgdorferi or I. ricinus bites (or both) are important regulatory factors in the transmission cycle(s) of B. burgdorferi.

Infection and stage conversion during murine pulmonary toxoplasmosis: a study with three different strains of Toxoplasma gondii.

A murine model of pulmonary toxoplasmosis was examined morphologically and immunochemically using 3 strains of Toxoplasma gondii. BALB/c and NMRI mice were infected with tachyzoites of a virulent strain (RH) or with brain cysts of an avirulent (GAIL), or moderately virulent, strain (NED). Depending on the strain of T. gondii, the degree of infection, number of parasites, and replicative potential of T. gondii in lungs varied. In lungs of mice infected with the RH strain, the number of parasites increased in mice during the survival period. Only tachyzoites were found, as confirmed by stage-specific monoclonal antibodies. In lungs of mice infected with the GAIL strain or the NED strain, different stages of parasites were detected. Up to day 14 after infection, only tachyzoites were present, followed by bradyzoites between days 14 and 20 after infection. The number of cysts decreased and finally could not be detected in this organ. In general, the number of cysts that developed in the lungs was smaller than the number that developed in the brain.

Is stage conversion the initiating event for reactivation of Toxoplasma gondii in brain tissue of AIDS patients?

Reactivation of chronic toxoplasmosis resulting in Toxoplasma encephalitis (TE) is a common event in acquired immune deficiency syndrome (AIDS) patients. Conversion from Toxoplasma gondii bradyzoites to tachyzoites is a prerequisite for reactivation. Until recently, the study of stage conversion in human tissue was not possible due to the lack of antibodies that recognize stage-specific epitopes after long-term formaldehyde fixation. Using the combination of a polyclonal anti-T. gondii antibody, the cyst-stage-specific monoclonal antibody CC2, and a tachyzoite-specific polyclonal antibody (anti-SAG1, recombinant), we tried to demonstrate parasite differentiation in the brain tissue of 10 AIDS patients with clinically suspected TE. Double labeling of the stage-specific antibodies enabled us to demonstrate interconversion between tachyzoites and bradyzoites for the first time in human tissue. The study confirmed that the transformation process is nonsynchronous and that the manifestation of TE depends on the degree and site of tissue destruction caused by invading tachyzoites. The original source of tachyzoites could never be located, but a few samples suggested that tachyzoites may invade by dissemination across the blood-brain barrier. Cyst rupture as the first event in the process of reactivation was not seen. We conclude that the initial site(s) of reactivation will be destroyed by tissue-destructive tachyzoites long before clinical symptoms occur.

The necessity to develop drugs against parasitic diseases.

This review focuses on the most significant trends in the development of drugs for the treatment of malaria, African sleeping sickness and toxoplasmosis. In the case of malaria, those include new fixed-dose artemisinin combinations, antifolates and new targets in the apicoplast of Plasmodium falciparum. Targets in the treatment of trypanosomiasis are the biosynthesis of glycosylphosphatidylinositol and enzymes involved in the biosynthesis of trypanothione. Efforts to develop a vaccine against toxoplasmosis are discussed as well.

Opportunistic infections caused by protozoan parasites.

Parasitic protozoa have played a major role in the discovery of the HIV epidemic. It was the occurrence of clustered cases of Pneumocystis pneumonia which caught the attention of the epidemiologists indicating that something unusual was going on. Very recently remarkable progress was made in understanding the epidemiology. Knowledge is evolving that Pneumocystis is host-specific to an extent which seems to justify species rank for the cause of death in AIDS patients for many years. Toxoplasma gondii infections were also recognized very early in AIDS patients. Cerebral toxoplasmosis has now replaced Pneumocystis pneumonia as a fatal infection in many cases. AIDS patients with CD4 cells below 200/microl have a high risk to develop this complication. Cryptosporidium parvum was recognized as the cause of diarrhea in AIDS patients and also in immunocompetent humans where it only leads to a diarrheal episode lasting a few days. In AIDS patients the persisting diarrhea leading to loss of fluid and electrolytes can be life-threatening. Another group of parasites previously unknown to infect humans are the microsporidia, which are wide-spread parasites in nature. Increasing numbers of such infections are observed but many questions regarding pathogenesis and epidemiology are still unclear.