Search

This article is a condensed review of the medically relevant protozoa in Central Europe and the infections and diseases caused by them. Information is given on modes and sources of infection, organs involved in the disease, prevalence, diagnostics, therapy, and prophylaxis. Moreover, travel-associated infections with protozoa are briefly outlined.

Infectious diarrhea belongs to the most frequent infections worldwide and can be elicited by a wide array of microbial pathogens. In developed countries transmission occurs much more frequently from contaminated food as compared to direct person-to-person contact, except for enteric viruses which can also be transmitted by aerosol formation after vomiting. In Germany, more than 90% of cases are caused by the four pathogens Norovirus, Rotavirus, Campylobacter and Salmonella. Therapy of infectious diarrhea is mainly supportive. In cases with a severe or prolonged course, signs of inflammation, bloody stool, immunosuppression, comorbidity and in suspected outbreaks, fecal microbial analysis should be performed and a specific therapy should be considered if indicated.

Human- and veterinary important parasites of the subkingdom of protozoans and helminths infect humans and animals by ingestion of parasites in contaminated water. The parasites are excreted from the body of infected humans, livestock, zoo animals, companion animals or wild animals in the feces. Recreational waters, agricultural practices and wild animals serve as vehicles of transmission of the parasites in the water supplies. The following topics are addressed: a) the life cycles of parasitic diseases-causing agents with proven or potential transmission via water b) the development and the current research status of the analytical techniques for the detection of parasitic diseases-causing agents from water c) the occurrence of Cryptosporidium and Giardia in surface water supplies and in treated water d) the possible water sources and transmission ways of the parasites into the water supplies e) the behaviour and the possibilities for the removal or elimination of the parasites by water treatment.

Intestinal protozoan disease diagnosed in pregnancy is mostly controlled by symptomatic treatment. Specific therapy can be delayed until after delivery. Only severe cases, i.e. continued diarrhea leading to malnutrition of either mother or fetus, require an immediate specific drug therapy, which might be harmful to the fetus due to toxic and teratogenic potentials. Vertical transmission of intestinal protozoa has not been described. Invasive protozoan infections can be lethal to the mother making immediate drug therapy mandatory, even if the potentials of fetotoxicity or teratogenicity are known. Vertical transmission occurs independent of maternal symptoms, causing clinical disease in the child either directly after birth or during the first months of life. The knowledge of endemic regions and of the maternal travel history is essential for early diagnosis and treatment of protozoan disease in pregnancy and of congenital protozoan infections.

Causative agents of intestinal infections in humans are about 10 pathogenic or facultative pathogenic species of protozoa of which Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum and Enterozytozoon bieneusi are discussed. G. lamblia from humans is morphologically indistinguishable from Giardia isolates originating from several species of domestic and wild mammals. Swiss Giardia isolates of human, sheep, cattle and dog origin could be transmitted to Giardia-free rodents and were rather homogenous in biochemical parameters. These data support the hypothesis that zoonotic transmission of Giardia may occur. Routine faecal examinations in Zürich in 1991 revealed 3.61% of Giardia excretors among 5017 examined patients. Of the same group of persons 3.95% excreted E. histolytica. At present it is anticipated that the species E. histolytica consists of invasive and non-invasive strains which can be differentiated by isoenzyme electrophoresis. The confirmation of this assumption could deeply influence the opinion about medical and epidemiological significance of Entamoeba infections. Cryptosporidium parvum is an important cause of diarrhea in HIV-infected patients. Person-to-person, zonnotic and waterborne transmission may play a role. A short review of new data on Enterozytozoon bieneusi and other microsporidia is presented. E. bieneusi appears to be an important causative agent of diarrhea in HIV-infected persons.

The importance of the mite Laelaps agilis (Parasitiformae) for the transmission of the Hepatozoon species living in the blood of Apodemus sylvaticus and Apodemus flavicollis (Hepatozoon sylvatici) is examined. With this mite the experimental transfer of the parasite to bred hosts of the same species was successful five times; for once, the transmission to a non-specific host (Clethrionomys glareolus) was also possible. Besides, an eventual stimulating effect emanating from the gonads of female mites to the development of parasites can be considered. Differences in the morphology of schizonts in the bone marrow and in the liver of infected Apodemus flavicollis are especially pointed out.

The incidence of Hepatozoon erhardovae in the blood of bank voles (Clethrionomys glareolus) captured in the investigated areas is examined. The biology of schizonts, their distribution in the lobes of the lung and the further development of natural infections in vertebrate hosts kept strictly free of ectoparasites are observed. The accumulation of gametocytes in larvae of the tick Ixodes ricinus and of the mite Neotrombicula zachvatkini after sucking on strongly infected bank voles is pointed out. Occasionally a parasitaemia is produced in the non-specific host (Apodemus flavicollis), but only with a specific transmitter (Megabothris turbidus).

A summary is given on the local and general risks of blood donation for the donor and especially on the recipient's risks to blood transfusion itself, including massive transfusion. The transfusion reactions are grouped in (1) risks in connection with the technique and physics of transfusion (cooling, air embolism, microaggregation, circulatory overload), (2) biochemical-metabolic risks (citrate intoxication, acidity, coagulation deficiencies), (3) immunological-serological risks (allergic and hemolytic reaction, addendum: pyrogenic reaction), (4) dangers of infection (bacteria: septic-toxic reaction, protozoae: malaria, viruses: herpes group, cytomegaly, hepatitis). In order to cut down the overall frequency of transfusion reactions, the use of blood derivatives instead of whole blood has been described.

Cat faeces can contain pathogens of zoonoses (viroses, bacterioses and protozooses) and stages of parasites (e.g. helminths) which can be spread potentially by Diptera. In reference to this: Remarks on the cat faeces. Spots of defecation of cats in different biotopes of the open land and in buildings. Conditions for the visit of Diptera to cat faeces. List of the 187 species of Diptera of 27 families discovered on cat faeces. Relation of the number of species being vectors found on faeces of cats to the entire number of species found on faeces produced by different carnivorous, omnivorous and herbivorous animals. 84.8% of the dipteran species ascertained on food and folder were also found on the faeces of cats, a remarkable hygienic result, perhaps caused by the composition of the dipteran fauna in the vicinity of traps. Remarks on the species of Diptera on faeces of cats which are vectors of diseases. Cat keeping and hygiene in buildings. Unhygienic and mass keeping of cats (e.g. breedings, laboratory keeping, animal-homes, zoos) may be a potential starting point for the attack of food and fodder by Diptera contaminated but also localities for the transmission of such diseases.