Observations on the course of Hymenolepis nana infection in immunosuppressed mice are presented. Treatment of the host with hydrocortisone acetate caused superinfection of the bowel with worms and the development of normal cysticercoids in the mesenteric lymph node and liver. Natural infection of mice deprived of their T-cells by pre-adult thymectomy and administration of antithymocyte serum resulted in superinfection and widespread metastasis of aberrant cysticercoids that were greatly enlarged and without scolices, causing death after about five months. The significance of these findings and their possible relevance to human infection with H. nana are discussed.

Lobatostoma hanumanthai n.sp. is described from the intestine of the carangid Trachinotus blochi from Bay of Bengal. It anatomical characters are compared with previously described species in the genus. This is the first record of an aspidogastrean from marine fishes of the Indian region.

The effect of existing Brugia pahangi infections on the establishment of a subsequent population was studied using jirds which had pre-challenge infections of 4 and 8 months duration. Necropsies were performed 28 days post-challenge inoculation in order to separate challenge and initial worm populations. The results indicate that existing infections of 4 or 8 months duration increase the susceptibility to subsequent homologous infections. The location of challenge population worms in tissue sites examined did not differ significantly between previously infected and uninfected groups. Previous infections did not affect the early growth of challenge population worms as indicated by their length.

Two age groups of parasite-free lambs, 4 months and 8 months, were infected with 50 000 infective larvae (L3) of T. vitrinus. A further group of 8 month old lambs were infected with 250 000 L3 T. vitrinus. The lambs were slaughtered at intervals after infection, and the size and linear distribution of their intestinal worm burdens examined and compared statistically. After the 50 000 L3 infections, it was found that a higher percentage of the initial inoculum had become established in the younger lambs but that there were no differences between the intestinal distributions of the population in either age group.

After infection with 250 000 L3, the percentage of the larvae retained changed with time. Up to sixteen days post infection, 38% of the larvae administered were retained; thereafter the percentage fell to 22%. The linear distribution of the population in this size of infection showed that a significantly greater percentage was present between 4.8 and 7.2 metres distal to the pylorus when compared with that after infection with 50 000 L3.

Effective treatment of mice with six to eight week-old patent S. mansoni infections with any one of five schistosomicidal agents (Oxamniquine, Praziquantel, potassium antimony tartrate, Niridazole and Hycanthone) resulted in a reduction in the degree of resistance to homologous challenge in the treated animals when compared with the level of resistance to reinfection observed in untreated mice with intact primary infections. Mice challenged five to six weeks after treatment with Praziquantel, Niridazole or Hycanthone demonstrated a lower level of resistance than mice challenged within 10 days of the termination of the chemotherapeutic schedules. Direct comparison of Praziquantel with potassium antimony tartrate indicated that treatment with the former drug allowed retention of a greater level of acquired resistance than the antimonial in the immediate post-treatment period. Resistance to reinfection in Hycanthone-treated mice was not restored by intravenous injection of S. mansoni eggs before challenge.

The presence of precipitin antibody and soluble circulating antigen was demonstrated in sera of individuals with clinical filariasis by counterimmunoelectrophoresis. Antigens derived from Litomosoides carinii and antisera raised in rabbits to the adult worm antigens were used for the detection of antibody and antigen in human sera. Of 35 subjects, 2 had microfilariae in the peripheral blood, 9 soluble circulating antigen, 19 antibody in sera, and 6 had both antigen and antibody. It suggests that 5.7% of cases diagnosed as bancroftian filariasis by parasitological examination can be increased to 62.8% by serological means.

Euparadistomum is described from 7 species of small mammal in Malaysia. The worms display characteristics intermediate between E. buckleyi Singh and E. pearsoni Talbot particularly with regard to body shape and arrangement of vitelline fields. The nature of morphological variation is discussed and comment made on the possible life-cycle of the parasite.

Experimental infections of white laboratory mice and wild rats (Rattus rattus) with cercariae of Schistosoma mansoni of different descent, whether murine or human, demonstrate that there is no significant difference in the probability of maturation of these cercariae into adult schistosomes.

These results enable us to hypothesise that the reverse would be true, i.e. that cercariae of murine or human descent would be capable of infecting man with the same success rate.

Circulation of the parasite from man to the rat and from the rat to man may therefore occur in natural habitats, which does not mean that rodents can maintain indefinitely and independently Schistosoma mansoni, nor does it mean that murine strains may not evolve locally.

Incidence of mating pairs in 40 worm infections in 5 week old female CBA mice increased up to day 30 post infection. By this time, and thereafter until the experiment ended on day 70, approximately 60% of the worm population occurred as mating pairs. Mating began during the ontogenetic migration of the worms. There was no difference between the percentage of worms mating in the more highly populated anterior sections of the small intestine as compared to the less densely populated more posterior sections. Significantly more female than male worms were recovered between days 8 and 20 post infection (p<0.02 to 0.001) and there was a significant decline in overall recoveries during the experimental period (r = −0.77, p<0.01). Low intensity infections, with 4 to 16 worms per mouse, demonstrated that a larger percentage of worms in the infection were mating at an earlier time post infection than in the 40 worm infections. Ontogenetic migration was reduced in low intensity infections because the initial distribution of worms was more restricted.

Phaneropsolus mulkiti sp. n. is described from the sand lizard Liolepis belliana Gray, 1827 from Bukit China, West Malaysia. Morphologically it is separate from all reported species of the genus Phaneropsolus Looss, 1899 and is the second species reported from a poikilothermic host.

The infective larvae of Nematospiroides dubius were exposed to various levels (0–30 krad) of gamma irradiation by means of a Cobalt 60 source. Groups of mice were infected with these larvae and autopsied 5 weeks later for worm counts. It was found that male worms were more susceptible to irradiation than female worms. In both instances, however, the survival curve on a semi logarithmic plot was characterised by a shoulder at low doses and an exponential component at the higher levels of exposure. No male worms were recovered from mice infected with larvae given more than 12 krad but some female worms were capable of surviving 20 krad. The fecundity of female worms was reduced by 61% at 4 krad and totally ablated at 8 krad.

Further experiments demonstrated that the survival of irradiated N. dubius in vivo was related to the extent of the damage caused at the time of irradiation and was not dependant on additional host parameters. Thus neither the number of irradiated worms inoculated nor the sex of the host radically altered the sex ratio or proportion of the worms lost as a result of irradiating the larvae. Furthermore, treatment with cortisone or sublethal irradiation of the host did not increase the proportion of surviving worms. It was, therefore, concluded that a host immune response was not involved.

Spirocamallanus papillicaudatus n. sp. from Pomadactylus oligodon, S. partitus n.sp. from Pomacentrus partitus, S. spinicaudatus n. sp. from Holocentrus marinus and S. garnotus n.sp. from Halichoeres garnoti are described from marine fishes of Puerto Rico which is recorded as a new geographical locality for the genus Spirocamallanus. S. plumierus n.sp. is described from a marine fish, Diapterus plumieri, of the Golfo de Cariaco, Cumana, Venezuela. These new species are distinguished from the known species mainly on the basis of number and arrangement of caudal papillae and different body measurements.

Quantitative examinations for the distribution and density of microfilariae were carried out on male Guatemalan onchocerciasis patients by taking 6 or 13 skin biopsies each from 74 subjects. We found that microfilariae were distributed most frequently on the iliac crest and secondarily in the scapular region; higher detection rates and greater microfilarial densities were seen in these areas. From these results we recommend the taking of biopsies from both of these anatomical regions so as to avoid false negative cases. The infected patients were classified into 3 groups (light, moderate and heavy infections) on the basis of the numbers of negative skin snips out of the 13 biopsies taken. In heavy infections, a higher densities of microfilariae were detected in the head and neck regions, as compared with the densities in the lower extremities (calf). The high concentration of microfilariae in these regions is of importance in relation to the development of eye lesions and/or transmission. Of patients who had microfilariae in the anterior segment of the eye some had negative skin biopsies from the outer canthus, retroauricular region and neck.

Inorganic substances play a significant role in the physiology of parasites and their importance, especially to gastro-intestinal parasites, is also demonstrated by the influence of mineral deficiencies in the host's diet (see Von Brand, 1966).

Collyricloides massanae (Trematoda: Collyriclidae) is described from cysts in the wall of the small intestine of a starling (Sturnus vulgaris L.) in the Netherlands. The original description was from a yellow necked mouse, Apodemus flavicollis (Melchior), so this is the first record of this species in birds.

Neocamallanus bareilliensis n. sp. has been described from the intestine of a freshwater fish Channa punctatus from Bareilly (U. P.) India. It has been distinguished from the other three species of the genus reported so far.

Proteocephalus pentastoma and Polyonchobothrium polypteri are redescribed from specimens from Polypterus spp. in the Sudan. Proteocephalus pentastoma is considered to be a valid species.

Necator americanus, originally isolated from man, developed completely in infant rabbits (RSG-1). This infection was serially passed in infant rabbits up to the 6th generation without using any immunosuppressant. Two day old infant rabbits demonstrated a high degree of susceptibility to N. americanus. Studies revealed the retention of worms in the intestine for more than 150 days during which egg production was high. In this experimental model the leukocyte, antibody and serum protein responses due to N. americanus infection were monitored. Results showed that eosinophil numbers rose significantly from day 28 to 170. A maximum was observed on day 80 (41%) in rabbits of the fourth generation. Antibodies to N. americanus were detectable in infected rabbits by counterimmunoelectrophoresis using third stage larval antigen (Rabbit strain). Generally, total globulins increased with decrease in albumin. Serum protein increase was associated with alpha-2, beta and gamma globulin components.

Three groups of golden Syrian hamsters received intraperitoneally either, (1) 1 × 107 spleen cells, (2) 0.5 ml. serum or, (3) 1 × 107 spleen cells plus 0.5 ml. serum, from donors infected 6 weeks previously with 25 Opisthorchis viverrini metacercariae, one day before and at the same time as challenge with 25 metacercariae. Three groups of control animals received the same quantities of spleen cells, serum or an admixture of both from normal non-infected donors in the same manner followed by challenge with 25 metacercariae.

Animals were killed six weeks after challenge, livers and extrahepatic biliary systems carefully removed, and liver worm burdens estimated. Additionally, parasitic egg counts were performed on pooled faeces samples collected one hour prior to death.

Animals receiving spleen cells, serum, or an admixture of both, from normal non-infected donors had mean worm burdens of 11.44, 12.00 and 12.66, respectively. Animals receiving spleen cells, serum, or both, from infected donors had mean worm burdens of 9.88, 7.77 and 12.00, respectively. There were no significant differences in mean worm burdens between control and experimental groups. However, a substanial reduction in parasitic faecal egg counts and subsequently mean egg production per worm was observed in all 3 groups of animals receiving spleen cells, serum, or both, from infected donors when compared to their respective control group.

These findings are discussed in relation to adoptive transfer studies performed with other helminths and their possible relevance to naturally acquired immunity is commented on.

Owing to the close association and proximity of man with his domestic animals (in particular the dog and cat), there exist the possibilities of human infection by certain helminth parasites of these animals which may, in some circumstances, lead to serious problems of public health, e.g. encephalitis and granulomatous lesions of the eye caused by toxocariasis (Ashton, 1960; Woodruff et al., 1964).