Restriction endonuclease analysis of mitochondrial DNA was carried out in order to differentiate diploid and triploid types of Paragonimus westermani originating from Japan. It was found that out of 16 restriction enzymes. PstI, HaeIII and RsaI revealed consistently different cleavage patterns between the two types.

Migration and development of the larvae of Gnathostoma nipponicum in the rat as second intermediate or paratenic host and the weasel as definitive host were examined to clarify the pathogenesis in each animal. The advanced third-stage larvae (AdL3) given orally to rats remained in the stomach for 12 h post-infection (PI). After that, larvae transiently invaded various organs and finally moved into the muscle within 48 h. The percentage of eosinophils in the blood taken from the jugular vein of rats infected with AdL3 reached a maximum (about 6%) on day 20 PI and then decreased. IgG antibody titre for G. nipponicum measured by ELISA began to increase on day 5 PI and reached a plateau on day 20 PI. The AdL3 given orally to weasels moved from the stomach into the muscle and then increased in size. Half of them invaded the muscle within 5 days, whereas the majority of them invaded the muscles within 20 days PI. Morphology of worms which invaded the muscles indicated that they were still the larval form with three rows of hooklets on the head bulb. The larvae in the muscles developed to young adult worms with seven rows of hooklets on the head bulb within 40 days PI. These young adult worms invaded the oesophageal wall and formed a tumour within 60 days PI. It was presumed that worms invaded the oesophageal wall though the adventitia. Ferret and mink were shown to be potential final hosts of G. nipponicum.

Detailed studies were carried out to assess the infection characteristics of the antelope schistosomes in BALB/c mice and Mastomys coucha. Both schistosome species reached sexual maturity in these hosts. However, they differed markedly in terms of egg production rates and preferred sites of tissue egg deposition. Tissue egg deposition commenced between 4 and 5 weeks in the case of Schistosoma margrebowiei and between 6 and 7 weeks in the case of S. leiperi. Tissue egg accumulation rates of S. leiperi were calculated to be 334 and 311 eggs/gravid worm pair/day in mice and M. coucha, respectively. The fecundity of S. margrebowiei was found to be substantially greater (approximately 5 times; daily output ranging from 1600–1900 eggs/gravid worm pair). While S. leiperi infections remained relatively stable in both hosts during the study period (i.e. up to 15 weeks after onset of egg laying), S. margrebowiei infections were observed to deteriorate rapidly in M. coucha.

The population dynamics of Labratrema minimus (Stossich, 1887) metacercariae (Trematoda, Bucephalidae) were studied in its second intermediate fish host Atherina boyeri from Salses-Leucate lagoon (Northwest Mediterranean Sea, South of France), during the cercarial shedding period. The infection parameters (prevalence and mean abundance of infection) showed the high susceptibility of silversides (juveniles and adults) to infection. The observed variation in the mean abundance of infection with respect to time and host size was explained by (i) the susceptibility of A. boyeri to multiple successive infections (increase in abundance of infection with host length and raising of parasite burden until August) and (ii) the loss, probably by more rapid death, of heavily infected silversides from each host size group (decrease in abundance of infection in September within each host size group, stability of the parasite burden within the older class of hosts over the whole period, premature decrease in the condition factor in August). Finally, it was deduced that the infection pattern observed over the May–September period was a dynamic process controlled by: availability of infective cercariae, influx of newborn silversides free of metacercariae until September, high susceptibility of juvenile and adult A. boyeri to infection, metacercarial loss and probably by parasite-induced host mortality.

In order to investigate the experimental transfer of Paragonimus westermani from rodents to rodents following subcutaneous and intraperitoneal routes, 13 rats and 23 mice were inoculated with a total of 115 (1 mature and 114 immature) worms of P. westermani subcutaneously and intraperitoneally. The age of worms before transfer was 25–193 days. The transfer was performed immediately after worm collection from rodents which were killed at various intervals from 4 to 144 days after infection. The location, development and size of worms were recorded. An infection rate of 58% (or 21/36) was demonstrated in rodents after experimental transfer of P. westermani by intraperitoneal and subcutaneous routes. Twenty-seven worms were recovered, giving a worm recovery rate of 23.5%. The rate was significantly higher by the subcutaneous route (34.8%) than by the intraperitoneal route (20.7%) but no difference was found between mice (23.9%) and rats (23.0%). The sizes of worms in the abdominal cavity, pleural cavity and thoracic muscles of mice, and in the leg muscles of rats were much less than in the pleural cavity and lung cysts of rats. A mature worm (7×5 mm) and numerous eggs were found in the uterus and pleural cavity of one rat. It is evidence that these rodents are unfavourable definitive hosts of P. westermani, because the worm size, infectivity, maturation and egg production are usually very low. However, the worms are usually widely distributed in their rodent hosts and remain small in size for a long period. Therefore, these rodents are good paratenic hosts for P. westermani and can play an important role in infecting cats and dogs with P. westermani in the laboratory.

In a survey carried out in 1991–1992 in the town of Yirka in Northern Israel, 49 dogs were examined for Echinococcus granulosus infection and abattoir data, based on organs condemned for the presence of parasites, was collected. The presence of E. granulosus by arecoline test was demonstrated in 7 (14.2%) of the dogs examined, but no parasites were found in the intestines of five stray dogs shot in the area. A survey of sheep slaughtered in the local abattoir during a one-month period revealed Echinococcus cysts in 10% of the 255 animals examined. No Echinococcus parasites were detected in 21 dogs examined 3 months after the initiation of praziquantel treatment. Echinococcosis seems to be a very serious public health problem in Israel and a control programme needs to be given a high priority.

The miracidium of Transversotrema patialense (Digenea: Transversotrematidae) has 21 epidermal cells arranged in four tiers with an epidermal formula of 6, 9, 4, 2. The penetration gland is large, conspicuous, contains a posterior globular part with 6 prominent nuclei and opens out through 6 pores arranged in two lateral groups at the tip of the apical papilla. The miracidium lacks lateral papillae, possesses a well developed subepithelium, a pair of flame cells and a germ ball.

Analysis of Giemsa-stained mitotic metaphase plates of Microsomacanthus spasskii and M. spiralibursata (Cestoda: Hymenolepididae) revealed the diploid chromosome numbers for both species to be 2n=6. The karyotypes are remarkably similar in general morphology; they both consist of three pairs of metacentric or meta-submetacentric chromosomes graded in size from 4.3 to 7.0 μm. Slight interspecific differences exist in the position of the centromere of chromosomes of the pair 3. Based on existing chromosome data the possible pathways of the karyotypic evolution within the family Hymenolepididae are discussed.

Surface iodination, extraction and SDS-PAGE analysis techniques were employed to characterize and compare the surface polypeptides of two strains of Strongyloides ratti. Third stage infective larvae and parasitic adults of homogonic and heterogonic strains were studied using a variety of surface labelling procedures and detergents for the extraction of labelled molecules. Profiles obtained from SDS-PAGE analysis demonstrated that homogonic and heterogonic strains of S. ratti have identical surface antigens.

Adult Lymnaea truncatula were subjected to 10 days of experimental desiccation and then remained in water for 1 or 8 days before each was exposed to a single miracidium. The infection rate was lower in these snails than in infected controls that were not exposed to stress (52–54% vs 73%). The redial burden clearly decreased in stressed snails (18–25 rediae per snail) than in controls (43 rediae). This numerical decrease concerned essentially: i) live independent rediae of the first generation and the first cohort of the second generation, and ii) dependent rediae of subsequent generations. Mature rediae were more numerous in the first cohort of the second generation than in the other generations. Desiccation before exposure limited the size of the redial burden but placement in water for 8 days just after the stress attenuated the effects of this factor.

The cytological study of males and females of Trichuris muris (Schrank, 1788) revealed the diploid number of chromosomes to be 2n=6. The sex determining mechanism was XX♀/XY♂. All the chromosomes were subtelocentric. Sex chromosomes formed the smallest pair, but X and Y were difficult to distinguish morphologically. Chromosome changes during gametogenesis in both sexes followed a classical pattern except in the male prophase and metaphase I. Four male autosomes formed two bivalents, each with one proximal chiasma with strict localization, while sex chromosomes X and Y formed two univalents. Female chromosomes formed three rod bivalents type, which possessed three, two and two chiasmata.

The effects in vivo of 5, 10, and 20 mg/kg of luxabendazole (LBZ) on the tegument of Fasciola hepatica have been examined 48 h, 7 days and 14 days post-treatment of experimentally-infected rats. As early as 48 h post-treatment, the drug is shown to provoke significant damage to the tegument. The pathological phenomena characterizing LBZ damage are blebbing of the apical plasmalemma, formation of microvillus-like projections over the free surface, swelling of the basal infolds and stimulation of autophagy. The spines are often fractured; the tegument in the vicinity of spines seems more strongly altered than that in other foci. The basal layer is often changed, from increase of electron density to lack of integrity with the apical cytoplasm. The progress of the ultrastructural damage with time is not expressed. However, cytochemical data show that at longer post-treatment intervals the surface-coat structure becomes irregular and patches of ruthenium red positive material of variable thickness are focally accumulated. Only a slight dose-effect is noted 48 h after LBZ application when the alterations provoked by 5 mg/kg are less evident than those by 10 and 20 mg/kg.

A further modification of a lung perfusion technique was evaluated by examining the recovery rate of 14-day-old Dictyocaulus viviparus worms from the excised lungs of 15 dead bovine calves. Up to 89% of the total number of worms found in 12 l of perfused fluid was recovered in the first 4 l collected. The application of this observation will increase the efficiency of the routine laboratory diagnosis of D. viviparus infection.

It was determined to examine whether rats injected with non-viable oncospheres of Asian Taenia or Taenia saginata became resistant to challenge infection with eggs of Taenia taeniaeformis, since (a) metacestodes of Asian Taenia and T. taeniaeformis develop in the liver of pigs and rats, respectively, and (b) Asian Taenia and T. saginata have human origins. Rats injected intravenously or subcutaneously with complete Freund's adjuvant with non-viable oncospheres of Asian Taenia showed statistically significant resistance to challenge infection with eggs of T. taeniaeformis, whereas those injected with non-viable oncospheres of T. saginata did not show any resistance.

Angiostrongylus vasorum infection was detected for the first time in eight foxes (Dusicyon vetulus) captured in the south of the State of Minas Gerais, Brazil. Two crossbred dogs were successfully infected orally with larvae from the foxes' faeces.

A previously reported recombinant λ Ts39 fusion protein (FP) derived from Trichinella spiralis larvae was purified by affinity chromatography using an anti-β-galactosidase antibody conjugated column and the effect of FP on induction of a protective response in mice was studied. BALB/c mice were injected three times at weekly intervals with FP emulsified in an equal volume of Freund's complete adjuvant and one week after the last injection mice were each challenged with a lethal dose of 1200 L1 larvae of Trichinella spiralis. As a result, the FP induced significant protection. Mice were also infected orally with 250 L1 larvae each after injection of the FP. On the 35th day of infection, immunized mice with the FP harboured 78% fewer muscle larvae than saline controls. Also, the numbers of adult worms in the small intestine were smaller in FP injected mice than saline controls on day 6 and 9 of the infection. These results suggest that the recombinant λ Ts39 FP is a potentially valuable antigen for vaccine development.