The natural infection of tench by Asymphylodora tincae in a lake was studied during one summer season. The incidence of infection was 57%, the mean intensity about 50. The distribution of the digencans along the host's intestine showed a maximum in the second half; this could be modified by the presence of other helminth species. Tench caught in early spring and kept in the laboratory retained their natural infection throughout the summer. Starvation of hosts during two months caused disappearance of the infection. Experiments showed that metaecrcariae, introduced into the intestine of tench, can excyst within one hour. In vitro, cysts in contact with tench bile opened within 15 seconds. Bile of several other cyprinid fisli species caused excystment within 60 seconds. Asymphylodora eggs appeared in tench faeces 7 to 10 days after infection. Progenetic specimens of A. tincae probably disintegrate in the intestine of the tench and their eggs arc passed out with the faeces.

All the natural hosts of Onchocerca parasites are large animals (MULLI-R, 1979) andthere is, therefore an urgent need to develop a small animal model for onchoccrciasis,preferably one that employs a strain of inbred host. Rodents have been usedsuccessfully as experimental hosts for the microfilariac of O. guiturosa (sec NELSON et al. 1966), O. cervicalis (see RAbalais, 1974), O. armilluta (see EL Bihari & Hussein, 1975) and O. ijibsoni (see Beveridge et al., 1980) but there have been few publishedattempts to infect these hosts with infective-stage larvae.

Echinococcosis in man and animals has been reported to be endemic in the Middle East(MAIOSMAN et al., 1977). As a result of this report and recent interest by the WorldHealth Organization to define more clearly the problem of hydatid disease in theMiddle East, the incidence of hydatid cysts found at surgery and at autopsy in theNcgcv region of Israel was retrospectively examined for the years 1970–1979.

Trematodes of the family I Ictcrophyidac in man and carnivores were studied in Khuzcstan, south-west Iran.Hight hundred and eleven stool samples from a population of 3400 in 13 villages in a swampy area located incentral Khuzcstan were examined by the formalin-ether concentration technique. The following helminths were found: Ascaris lumbricoides 7%, Trichostronayius spp. 53%, hookworms 4%, Trichuris trichiura 5%, Hywenolepis nana 12% and hetcrophyid spp. 8%. Post-mortem examination of carnivores revealed that 14·2% of jackals, 33·3% of foxes and 2·5% of dogs were infected with hctcrophyids, namely Metagonimus yokogawai, Heterophyes heterophyes and H. katsuradai. The freshwater snails Melanoides and Melanopsis spp. and brackish water fishes ltarhus spp. and Mugil spp. were thought to be the intermediate hosts of these flukes in this area. This is the first report of hctcrophyid infection in man and carnivores in Iran.

A substantial level of resistance to a lictcrologous challenge with Fasciola hepatica was demonstrated insheep harbouring primary non-patent (two- to three-week-old) and newly patent (seven- to cight-wcck-old)Schistosoma hovis infections, the liver-fluke burdens being reduced by 70% and 93%, respectively, ( p< 0·01) inthese groups compared with that of the challenge control group.

The chemotherapeutic responses of three test nematodes, Nippostrongylus brasilietxsis, Nematospiroidesdubius and Ancylostoma ceylanicum to standard antihookworm drugs were assessed in order to select asuitable host-parasite system for the primary screening of potential antihookworm compounds. N. dubiusbehaved inconsistently and, with some infections, required more drug to achieve 100% clearance. Nippostrongylus brasiliensis was found to be sensitive to thiabendazole, tetramisole and levamisole but the broad spectrum anthclmintic mebendazole was ineffective. A. ceylanicum was very sensitive to mebendazole, sensitive to tetramisole and levamisole and refractory to thiabendazole. In vitro, none of the compounds had any lethal effect against any of the nematodes, except mebendazole against A. ceylanicum.

A. ceylanicum does occur in man and its chemotherapeutic reactions are similar to those of target hookworm infections of economic importance. As such, although not equally sensitive to standard anthelmintics, it is recommended for routine primary screening.

The reliability of Stoll's dilution egg count technique, Beaver's direct smear technique and Katz's modified thick smear technique were evaluated on patients with ascariasis. Studies revealed that the modified thick smear technique appears to be more reliable and accurate. The use of these three techniques revealed a significant correlation between the number of eggs per gram (e.p.g.) and worm load. Following the introduction of a standardized factor in a study of 30 patients with worm infections, a highly significant correlation was obtained between the e.p.g. and the worm load for all three techniques. The use of a Standardized Factor is recommended for better prediction of the worm burden. The results of this study reveal that a female Ascaris lumbricoides lays an average of 218,094 (range 82,251–365,200) eggs daily. The ratio of male to female A. lumbricoides was 1:1·4

Mice infected for one to eight weeks with Trichinella spiralis cleared either 51Cr-labelled sheep red blood cells (SRBC) or I-polyvinyl pyrrolidone (PVP) given intravenously. PVP was cleared more rapidly from the blood of mice infected for one week than from uninfected mice with older infections which behaved in a similar manner to the controls. SRBC were consistently cleared faster from the blood of mice infected for one week than from normal mice. If the infections were older than this a more rapid clearance was also demonstrated as long as the infections were reasonably heavy.

Remarkable hypertrophic changes were observed in the adrenal and thyroid glands of male mice after 7 to 16 days of infection with the filariform larvae of Ancylostoma caninum, but not in females. The adrenal gland revealed enormous enlargement of cells in the zonae glomerulosa, fasciculata and medulla, and also the formation of big vacuoles in the glomerular zone, whereas the thyroid gland showed distinctly hypcrtrophicd follicular epithelium with marked acolloidal condition and follicular mass formation. These changes in the cellular diameter were highly significant (P>0·001 to <0·005). The possible reasons for hyperactivity of these glands are discussed.