Natural selection should favour parasite genotypes that manipulate hosts in ways that enhance parasite fitness. However, it is also possible that the effects of infection are not adaptive. Here we experimentally examined the phenotypic effects of infection in a snail–trematode system. These trematodes (Atriophallophorus winterbourni) produce larval cysts within the snail's shell (Potamopyrgus antipodarum); hence the internal shell volume determines the total number of parasite cysts produced. Infected snails in the field tend to be larger than uninfected snails, suggesting the hypothesis that parasites manipulate host growth so as to increase the space available for trematode reproduction. To test the hypothesis, we exposed juvenile snails to trematode eggs. Snails were then left to grow for about one year in 800-l outdoor mesocosms. We found that uninfected males were smaller than uninfected females (sexual dimorphism). We also found that infection did not affect the shell dimensions of males. However, infected females were smaller than uninfected females. Hence, infection stunts the growth of females, and (contrary to the hypothesis) it results in a smaller internal volume for larval cysts. Finally, infected females resembled males in size and shape, suggesting the possibility that parasitic castration prevents the normal development of females. These results thus indicate that the parasite is not manipulating the growth of infected hosts so as to increase the number of larval cysts, although alternative adaptive explanations are possible.

Although several records now exist of the occurrence of Capillaria (Hepaticola) hepatica (Bancroft, 1893) as a natural infection of the wild rabbit the attempts which have been made to infect this host with eggs obtained from an infection in the rat have not been completely successful. Nishigori (1925) states that although this parasite can infect the rabbit and shew some development it does not reach maturity, while Saito (1925), in the English account of his paper given in The Japan Medical World states that “In the rabbit the larva might develop into maturity and cause pathological changes but do not multiply.”

Only five of the eight species assigned to the genus Paracooperia are considered valid and are redescribed. P. petrowi Memmedov, 1961 and P. indiana Ali and Deshpande, 1970 are considered synonyms of P. nodulosa (Schwartz, 1928) Travassos, 1937 and the synonymy of P. matoffi Le Roux, 1950 with P. nodulosa is confirmed. A key to the species of the genus is given and their hosts and geographical localities are listed.

A new genus and species of filarioid worm is described from the peritoneal cavity of fruit bats, Pteropus hawaiiensis from Fiji and the name Chiropterofilaria brevicaudata n. sp. is given to it. The microfilaria is described. This appears to be the first record of a nematode from this host. The new genus is differentiated from its nearest genus Lemdana in that the spicules are only slightly unequal; and in the female worms, the oesophagus usually make several turns around the vagina before joining the intestine. From the same host, a second microfilaria, Microfilaria fijiensis n. sp. is described, the adults of which were not found.

The breed differences in post-parturient rise (PPR) in faecal egg counts in lambing ewes of different breeds naturally infected with Haemonchus contortus were compared. The ewes of Nali, 50% Nali × 50% Russian Merino/Corriedale and 37.5% Nali × 62.5% Russian Merino/Corriedale were treated with fenben-dazole while ewes of the above three breeds as well as 25% Nali × 75% Russian Merino/Corriedale, were kept untreated. Observations from 3 weeks before lambing to 12 weeks post-lambing at weekly intervals revealed that in treated ewes, egg counts of Nali did not differ significantly with 50% Nali whereas 37.5% Nali had significantly higher egg counts than those of Nali and 50% Nali. In untreated ewes egg counts of 50% Nali were significantly higher than that of Nali on some occasions, while 25% Nali had significantly higher egg counts than the other three breeds. None of the ewes from the Nali breed showed signs of haemonchosis, whereas few lambing ewes of the three Nali crosses (50%, 37.5% and 25% Nali) showed signs of haemonchosis and one ewe of the latter breed died.

A simple method for the collection of third-stage larvae of Necator americanus has been described. This technique provides repeated recovery of very clean larvae from cultures in moderate numbers.

A new species of Dirofilaria, D. (Nochtiella) linstowi n.sp. is described from the subcutaneous tissues of the Grey langur, Presbytis entellus thersites, in Ceylon. The adult worms differ from the hitherto described African and South-east Asian species in several respects, especially spicule size and ratio, arrangement and number of caudal papillae and dimensions of the microfilariae.

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.

Examination of naturally infected felids and viverrids in Malaysia confirmed previously published records which indicated that P. westermani occured only in felid cats. Felis planiceps and F. temnickii were reported as new host records. Analysis of stomach contents revealed no crab remains in either family of cats, but confirmed that felids were strictly carnivorous while viverrids were often omnivorous. In feeding experiments, only viverrids ate the host crabs Potamiscus johorensis and Parathelphusa maculata. The probable transmission of P. westermani to felids via paratenic hosts was discussed.

In 1939 the sugar-beet nematode, Heterodera schachtii Schmidt, 1871, was found attacking the roots of sugar beets in the Blackwell district near Sarnia, Ontario. Studies were started in 1947 on the control and biology of this cyst-forming nematode, including the susceptibilities of various cultivated and weed plants to the nematode. Susceptibility was based on the presence or absence or degree of infestation of gravid white females on the roots.

1. Panagrellus silusiae was cultured in various media to determine the possibility of establishing it as a facultative parasite in the mammalian body. It was found to tolerate pH values of its environment between 1.0–8.5.

2. It survived for 24 hours in gastric juice but was rapidly killed by pancreatic juice. In both preparations larval mortality was higher than that of adults.

3. P. silusiae withstood environmental temperatures up to 87°C. At 40°C. death did not occur within 24 hours.

4. P. silusiae could survive without oxygen for at least 24 hours provided that the carbon-dioxide produced by its own respiration was not allowed to accumulate.

During studies on the ecology of fish helminths, the tapeworm Proteocephalus torulosus (Batsch, 1786) was frequently found in the intestine of the blue bream (Abramis ballerus) from the Oder River (Germany/Poland). In total, 633 fish, ranging between two and 16 years old, were sampled at monthly intervals over a two year period during 1993–1995. Statistically significant differences in the seasonal occurrence of the parasite in its fish host were observed. In 1993, the prevalence remained at a high level, ranging between 61.9 and 100%. During the summer of 1994, this value decreased to 5.5% and remained low for the rest of the year. The pattern of mean intensity of infection was similar to that of the prevalence. In 1993, the mean intensity varied between 8.4 and 31.8 worms per infected fish, with a continual loss of worms being observed in the summer of 1994. Changes in the amount of suspended particulate matter in water have been identified as the main cause of these observed differences in the course of infection of blue bream.

1. A new species, Ganeo bufonis, from a toad, Bufo viridis, in Kashmir, is described. This is the first species of the genus recorded from a toad; it differs from the known species in having both the vitelline glands confined to one side. The uterine coils do not extend into the post-caecal area; the excretory bladder is without any median stem and the metraterm is present.

2. Ganeo tigrinum Mehra and Negi, 1928 is also recorded for the first time from Bufo viridis. Ganeo kumaonensis Pande, 1937 and Ganeo lingnanensis Li, 1938 are both regarded as synonyms of Ganeo tigrinum.

3. A revised generic diagnosis and a key to the species of the genus Ganeo Klein, 1905 are given.

The biochemistry and histochemistry of Pegosomum egretti have been studied using standard techniques. Phosphatases were analysed colorimetrically; the optimum pH for acid phosphatase activity was 5·0 and for alkaline phosphatase was 10·0. The results were compared with those of other trematodes. Histochemical localization of acid and alkaline phosphatases revealed differences in enzyme activity in various tissues. These differences in the site and pattern of distribution of the two enzymes have been discussed in relation to transport of raw materials and the metabolism of the cell concerned.

The survival characteristics of Cercaria chackai, the larval form of the curious ectoparasitic digenetic trematode Transversotrema chackai, in sea water, sea water diluted with deionized water in different proportions, deionized water, pond water and tap water were studied. Naturally shed, fresh cercariae had the maximum life span of 20 h 40 min in pond water at salinity 17·8‰, pH 6·45, O2 5·76ml/l and temperature 31·5°C. With increase in salinities beyond 17·8‰, survival time was drastically reduced and beyond 23·58‰,, was restricted to a few minutes. In sea water with a salinity of 38·3‰, the maximum survival time was only 8 min. Below 17·8‰ salinity, although the survival time was less, the difference was not very marked and even in tap water with no salinity, the cercariae lived up to 19 h 50 min. In deionized water the maximum survival time was only 3 h 15 min. Since pond water at pH 6·45 allowed maximum survival time, it is presumed that the cercariae preferred a slightly acidic medium. As temperature was maintained constant and oxygen was available, neither of these two factors, apparently, affected the survival pattern. It is concluded that C. chackai is a typical freshwater form showing considerable tolerance to fluctuations in salinity although the family Transversotrematidae is considered to have a marine origin.

Tetrameres fissispina (Diesing, 1861) is recorded for the first time from the Wood-Pigeon, Columba palumbus L., and Stock Dove, C. oenas L.

An account is given of a natural infection of Wood-Pigeons with T. fissispina during the winter months of 1962/63 and 1963/64 in Cambridgeshire.

Inbred jirds (Meriones unguiculatus) were divided into three groups; each animal in two of the groups was infected with 30 infective larvae (L3) of Litomosoides carinii. When these infections were patent, the jirds of one of the two infected groups plus those of the third group were injected with 30 L3 L. carinii each. All animals were killed either on day 14 or 24 after the second infection for the recovery, enumeration and measurement of all worms and developing larvae. Challenge larvae were stunted (smaller) and fewer than control larvae. Additionally, fewer challenge larva were recovered on day 14 than on day 24, indicating that migration to the pleural cavity was retarded.