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Genetic variation in 25 Cryptosporidium isolates was analyzed using the random amplified polymorphic DNA (RAPD) technique. Simple reproducible polymorphisms were generated (using five primers) from Cryptosporidium DNA that was free of contaminating bacterial DNA. The results generated by four of the five primers were statistically correlated (P < 0.001). The combined data from three primers were used to construct a phenogram using Jaccard's distance. Four groupings could be distinguished. Two C. serpentis isolates from snakes formed a distinct group of their own, whereas C. parvum isolates were divided into two main groups: one containing most human isolates and the other containing mostly domestic animals plus two remaining human isolates. Due to the sensitivity of the RAPD technique, isolates can now be analyzed genetically, directly from fecal samples without further biological amplification. This represents a significant advance on current techniques.

Fourteen Giardia duodenalis isolates were examined using the RAPD (random amplified polymorphic deoxyribonucleic acid) technique. Simple reproducible polymorphisms were generated using 3 different RAPD primers. The results generated by each primer were very similar and were significantly correlated with each other. These data were then compared to existing isoenzyme electrophoresis data on the same isolates. The RAPD data divided the isolates into 10 groupings or rapdemes while the isoenzyme data divided them into 10 similar zymodemes. Both methods grouped 4 isolates (BAH42, BAH44c9, BAH12c9 and BAH39c7), which comprised a phenotypically heterogeneous assemblage with respect to growth rate and metabolism, into similar groupings. The 2 methods were significantly correlated (P < 0.001). It will therefore be possible to use RAPD for the characterization of isolates of Giardia, and other parasites such as Cryptosporidium, which are refractory to cultivation in vitro.

Previous studies in our laboratory have shown that albendazole is effective against Giardia spp. in vitro and in vivo, prompting an investigation of the effects of several related benzimidazoles (BZs) on the viability of this protozoan parasite. A range of BZs was tested, and their effects were compared with those of a number of microtubule inhibitors. The effects produced by the two types of drugs were markedly similar, namely, trophozoite detachment and distortion of morphology and general structure, indicating a potential antimicrotubule mode of action for BZs. Mebendazole, albendazole, and fenbendazole proved to be among the most effective BZs tested, exhibiting apparent irreversibility. Nocodazole, oxfendazole, and albendazole sulfoxide, among others, produced transient inhibitions only. Further studies are required to evaluate all available BZs and other antigiardial agents to ensure the development of the most effective and safest antigiardial agent possible.

The morphology, adult development and genetic characteristics of Echinococcus granulosus isolated from pigs in Poland were examined and compared with those of other recognised strains of E. granulosus. The isolates were characterised by their distinct morphology, rapid maturation and unique DNA hybridisation profiles. The form of E. granulosus that occurs in European pigs may therefore be a distinct strain that can be separated morphologically and genetically from other strains and that exhibits features of epidemiological significance, including a rapid rate of development in dogs and an apparent low infectivity to humans and domestic ungulates.