Guineapigs infected with a lethal dose of Ascaris eggs died between the fifth and tenth day of infection. The M.L.D. was found to be 20,000 eggs. The clinical symptoms and the macroscopic lesions in the liver and lung are described. Infected guineapigs developed an active acquired immunity and repeated infection conferred a high degree of resistance on animals which were subsequently reinfected. Resistance was manifested by the survival of the host following a lethal dose of eggs, and by an inhibition of larval migration. (Less haemorrhage was found in the lung, and fewer larvae were recovered from the lungs and tracheae, after reinfection than following one infection).

The M.I.D. against a reinfective lethal dose 18 days after infection was 500 eggs. The smallest immunizing dose required to give resistance to a challenge 51 days later was 10,000 eggs. This suggests that the resistance manifested at three weeks is greater than that shown after seven weeks, i.e. there is a waning of the immunity.

Buckley and Fairley (1950) working in England found segments of a species of Bertiella passed by an eight year old girl who had lived in Kenya for 14 months during 1946–47. Since only the terminal segments were available for study, a specific identification could not be made, though the authors thought that it was probably Bertiella studeri (Blanchard, 1891). Nelson (1963) has found that baboons in Kenya are commonly infected with species of Bertiella.

Guineapigs infected by mouth with eggs of A. suum developed an acquired resistance to reinfection 27, 35 and 51 days later. Resistance of the host was manifested by: survival following a lethal dose of eggs; an inhibition of larval migration; a retardation of larval growth; and the ability to maintain or gain weight.

By means of the conglutinating complement absorption test, using a saline extract of worm as antigen, antibodies were detected in the serum of resistant guineapigs seven days after the second reinfection. Antibodies were not detected in the serum of nonresistant guineapigs seven days after one infection. There was some evidence to indicate that the conglutinating antibody titre of the serum is a measure of the host's ability to resist infection.

Seven males and three females, identified as Trichostrongylus hamatus Daubney, 1933 were recovered from the abomasum of a steinbok shot at Deloraine Estates in the Kenya Highlands. No other Trichostrongylus species was present. The species was originally described by Daubney (1933) from Ovis aries also from the Kenya Highlands. The specimens from the steinbok were examined and compared with the original description of the species. Figs. 1–4 show drawings of the spicules and part of the bursa. Table I gives the measurements of Daubney's specimens compared with those of the present specimens.

Antibodies were demonstrated in the sera of rabbits experimentally infected by mouth with the eggs of A. suum.

An alcoholic extract of freeze-dried ovaries, oviducts and uteri of adult female Ascaris worms was used as an antigen in the complement fixation test, and a polysaccharide fraction and a saline extract of whole worms were used as antigens in the conglutinating complement absorption test.

In all rabbits the pattern and nature of the antibody response was similar using the three different antigens. When the saline extract antigen was used in the C.C.A.T., antibodies were detected earlier, and titres were recorded higher, than when other systems were used. The degree of response was proportional to the size of the infective dose. Circulating antibody first appeared between the third and eighth days of infection. The highest concentration of serum antibody was reached between the eighth and twenty-first days, and in those animals which received large doses the maximum response occurred about the third week. By repeated twice-weekly infection antibody was demonstrated in the serum for 114 days.

Stephanofilaria dinniki sp. nov. is described from cutaneous lesions of the black rhinoceros, Diceros bicornis L. The species differs from the others of the genus mainly in the length of the left spicule in the male; the short distance of the vulva from the anterior end in the female; and the curved tails in both sexes.

1. A new trematode Tremajoannes buckleyi gen. et sp. nov., is described from the bats Pteronotus davyi fulvus and Mormoops megalophylla from Colombia, Central America. A comparison between Tremajoannes gen. nov. and the other related genera of the family Lecithodendriidae is given.

2. Primatotrema Premvati, 1958 is considered as a synonym of Phaneropsolus Looss, 1899, accordingly Primatotrema macacae should be Phaneropsolus macacae (Premvati, 1958), n.comb.

3. Phaneropsolus magnitesticulatus Ryšavý et al., 1960 is considered as a synonym of P. macacae (Premvati, 1958).

4. Phaneropsolus orbicularis (Diesing, 1850) Braun, 1901 is reported from a new host and redescribed.

A survey for parasites has been undertaken in 20 mountain gorillas (Gorilla gorilla beringei) from the Eastern Congo Kivu province.

Six full-grown (two males and four females), three adolescents (one male and two females), and eleven young gorillas were examined, some of them during several consecutive months. Nine autopsies were performed.

No protozoa were discovered in the blood. Plasmodium parasites which are common in gorillas and chimpanzees from West Africa were never found in the Eastern Congo primates, including ten other gorillas examined previously and some fifty chimpanzees. Severe diarrhoea with a balantidiasis picture developed in two young gorillas. Autopsy revealed however an intensive infection with Oesophagostomum stephanostomum and resulting fatty degeneration of the liver. Oligotrichida belonging to the genus Troglodytella were commonly found in the intestinal tract. Oesophagostomum stephanostomum eggs were consistently present in the stools of the gorillas and autoinfection caused the death of several young gorillas 4 to 6 weeks after their capture.

Recent collection of lung fluke material from hydrophiid sea snakes permits a reevaluation of the suitability of criteria separating the monotypic genera Pulmovermis Coil and Kuntz, 1960 and Hydrophitrema Sandars, 1960. Consideration is also given of the new subfamily Pulmoverminae, erected by Sandars (1961) to include these genera within the digenetic family Hemiuridae. Typographical errors in the original description of H. gigantica Sandars, 1960 have been corrected, reducing the gross or external measurements of that species by ten times. Validity of characters such as flexure of the body, location of testes and ovary with respect to body length, length of seminal vesicle compared to body length, and anterior extension of the seminal vesicle with respect to acetabulum have been rejected. Retained are general body shape, relative position of acetabulum and development of peduncle, degree of coiling of seminal vesicle, and tandem or oblique arrangement of testes. Characters newly employed include body length-to-width ratio and presence of a cuticular fold in Hydrophitrema enclosing both suckers. Retention of the present genera based on these revised characterizations is recommended. Subfamily criteria (form, structure, and size of seminal vesicle, shape of vitellaria) are similar to those employed among the other nineteen subfamilies of this large and possibly heterogeneous group. In addition, these flukes are unique within the family on ecological and physiological grounds, in that they parasitize the lungs of sea snakes rather than the stomach of marine fishes, the usual site and host for members of this family.

1. Chabertiella pesteri gen. and sp. nov. from the giraffe (Giraffe camelopardalis) is described.

2. Chabertia rishati Akhtar, 1937 is synonymized with Chabertia ovina (Gmelin, 1790) Railliet and Henry, 1909.

This paper concerns the relationships between miracidia of Schistosoma haematobium from Aden and various species of the Bulinus complex. It includes evidence on penetration and further development within the snail as revealed in serial sections.

1—A description is given of Buckleyuris buckleyi n.sp. from the steinbok, which is a new host for the genus.

2—The genus Salamia Sarwar, 1959 is synonymised with the genus Buckleyuris Sarwar, 1959.

3—A key of the different species of the genus is given.

During the course of studies on the mechanism of penetration by miracidia of Schistosoma mansoni into their intermediate hosts it was found that commensal annelids of the genus Chaetogaster frequently preyed upon the attaching larvae. Wagin (1931) found cercariae in the gut of Chaetogaster and Wesenberg-lund (1934) confirmed Wagin's finding. Wallace (1941) reported that these worms serve as second intermediate hosts for some trematodes and when cercariae of Trigonodistomum mutabile were ingested by Chaetogaster limnaei they penetrated the gut wall and encysted in the body cavity. When the worms with their metacercariae were fed to fishes the adult trematodes were later recovered. Ruiz (1951) working on Schistosoma mansoni noted that the Chaetogaster ingested the cercariae liberated from the snail. Khalil (1961) further noted when observing experimental infection of Lymnaea natalensis with miracidia of Fasciola gigantica that these worms ingested the miracidia, and he found that the majority of these worms had a variable number of miracidia in their gut.

1. Four worms were recovered from the subcutaneous connective tissue of a leopard. Of these two males and one female were identified as Filaria martis Gmelin, 1790 with the measurements given and a female described as a new species under the name Filaria russelli.

2. This finding is the first record of the genus Filaria Mueller, 1787 in a leopard.

A total of 431 rats, collected twice monthly during one year from the same locality (a slum-commercial area of approximately 1 km2 in the southern part of Tel-Aviv), were examined for the presence of S. ratti and S. venezuelensis. Of the 431 rats examined, 154 (35.7%) were found infected as follows: 48 with S. ratti, 37 with S. venezuelensis and 69 with both species. A seasonal fall in infection, from a high incidence of 78·9% in February to a low incidence of 4·5% in September was noted, which roughly corresponded to the monthly rainfall. The persistence of infestation throughout the rainless summer months is probably due to seepage from surface structures (warehouse depots, dripping outdoor faucets, faulty plumbing, etc.). The monthly incidence of both species of parasite according to age and sex of the host is discussed.

Two experiments are described in which antibodies against A. suum were detected in the circulation of infected pigs by means of the conglutinating complement absorption test. The pattern and nature of the antibody response was studied. In 21 out of 24 cases the sera antibody titres rose after test doses of infective eggs were given, and on 18 of these occasions a rise in titre was observed within seven days. Following infection two peaks of antibody were detected. At three to four weeks the antibody content of the serum reached its highest concentration, and a further rise was apparent between the 37th and 56th days.

The phenomenon of “self-cure” was demonstrated following reinfection. This was manifested by a depression of the egg count and the elimination of Ascaris worms from the intestine, with a concomitant rise in the antibody content of the serum.

In three out of five pigs which were initially infected, the infection became patent between the 51st and 58th days. On only one occasion out of thirteen were any superimposed larvae able to reach maturity.

Pigs which had been previously infected exhibited resistance to a challenge dose. This was shown by (1) the absence of clinical signs, (2) a resistance to larval migration, and (3) an inhibition of larval growth. In this demonstration of an active acquired immunity to A. suum infection in pigs, a correlation between resistance and high sera titres was observed.

Methods for isolating the various stages of parasite life-cycles in large amounts and in a clean condition for biochemical and immunological studies are urgently needed. Among the parasitic nematodes the methods so far developed mainly concern the adult worm, though the eggs of some of the Ascaroidea are notable exceptions. This paper describes adaptations of one of the traditional methods of culturing Nippostrongylus infective larvae which satisfy the needs of biochemical and immunological studies.

It was possible to make a more critical study of immunity against A. suum by infecting pathogen-free, colostrum-deprived pigs produced by hysterectomy.

By means of the conglutinating complement absorption test, using a saline extract of worm as antigen, antibodies were first demonstrated in the circulation of three experimentally-infected pigs between the 10th and 13th days of infection, and were detected in the sera of two of them for at least 97 days.

The infections did not become patent, and no acquired immunity was shown by the pigs against a reinfection 97 days later. There was no evidence of an age immunity against migrant larvae.

A rise in serum antibody was observed, within seven days of infection, in six pigs aged between 10 weeks and 11 months, following a test dose of 500,000 eggs. Three suckling pigs, aged three weeks, did not respond serologically within seven days to the same test dose.

Following the oral administration of third- and fourth-stage A. suum larvae, which had previously completed nine or ten days somatic migration in guineapigs, rabbits or a pig, six out of eight pigs showed a rise of serum antibody titre, as measured by the conglutinating complement absorption test using a saline extract of Ascaris worm as antigen. Four of these pigs had negative titres before infection, and in these animals antibodies were first detected between the 14th and 20th days. Maximum serum antibody concentration was reached between the 14th and 34th days of infection, and antibodies were detected for at least as long as 68 days.

Larvae were recovered from the faeces on the 23rd and 29th days of infection, and in two pigs out of eight the larvae reached maturity, eggs first being seen in the faeces on the 42nd day.

The results suggest that (1) Ascaris larvae, on their return to the intestine, release antigenic substances which are then absorbed by the gut wall to stimulate the production of antibodies; (2) the secondary antibody rise, which occurs about the sixth or seventh week of an infection with Ascaris eggs, is due to the absorption of this larval antigen; and (3) the moulting process (fourth moult) is not only an important stage for stimulating this further antibody production, but is also the time when maturing larvae are affected by the immune mechanisms of the host.

On reinfection with Ascaris eggs the phenomenon of “self-cure” was noticed. A fall in the faecal egg count, which became negative on the 21st day, was accompanied by a sharp rise in antibody titre. An increase in the number of infertile eggs in the faeces, rising from 11% on the day of reinfection to 100% on the 14th day, was also observed.