Rodents, particularly those belonging to the family Muridae, form the largest group of mammals in Malaysia. They are also a group that has been well studied because of their medical and economic importance. Yet, comparatively little is known, in Malaysia, about the helminths that are associated with them; far less the types of terrain in which these are prevalent. An attempt is now made to survey the nematodes parasitic in these rodents, with a view to assessing the potential risk from those that are harmful to man and domestic animals, and to studying those that are harmless, but nevertheless form an enlightening contribution to the knowledge of Malaysian parasitic fauna.

Identification of members of the family Schistosomatidae presents problems not only because of the imperfect state of their taxonomy, but also because no attempt has been made to collect and organise the available data. There are only two general keys on the schistosomes (Price, 1929 ; Yamaguti, 1958) both of which are incomplete. The result of this is that many authors, too numerous to mention, list genera which are no longer valid and erect new species without comparing them with species to which they are obviously closely related.

The normal ultrastructure of the fundic gastric glands of cattle is described and compared with those from calves infected with T. axei. Loss and alterations in structure of zymogen and parietal cells are observed and are related to changes observed by light microscopy. The significance of these changes is discussed.

About 100 specimens of the fresh-water snail, Melanoides tuberculatus (Muller), collected on 30th March, 1962 from “Kukrail”, a tributory of river Gomati, were examined for larval infection. One specimen was found infected with a unique cercaria belonging to the genus Transversotrema. The writer subsequently attempted to collect this cercaria from the same place and 1750 specimens of the said host were examined in the following years (1962–67) without success. Further, a large number of specimens of fishes of the genera Channa Gronov; Colisa Cuv. and Val.; Xenentodon Regan and Nundus Cuv. and Val., common in the tributary were also examined for metacercarial infection of this cercaria but none were found.

The normal ultrastructure of the abomasal fundic glands in sheep is described and compared with those of sheep infected experimentally with T. axei. Alterations were observed in mucous, mucous neck and zymogen cells and the results are compared with a similar study in normal and infected calves.

1. The susceptibility of two strains of rats, namely London-hooded and Wistar, to infection with S. mansoni has been investigated

2. Although equal numbers of cercariae penetrated the skin in both strains, recovery of worms was always higher from the London-hooded strain irrespective of the dosage level.

3. In both strains there was a significant relationship between body weight at time of infection and number of worms recovered. The correlation was a negative one, indicating that lighter (younger) rats were more susceptible than heavier (older) rats.

4. A rapid rate of elimination of infection was demonstrated in London-hooded rats between the 4th and 8th week after infection.

It is concluded that Bearup's cercaria, described from Pyrazus australis in Australia, is different from Cercaria variglandis; the former develops into Austrobilharzia terrigalensis and the latter into A. variglandis (Syn. M. Chapini Price, 1929; M. variglandis Stunkard and Hinchliffe, 1952).

Bearup's cercaria should be henceforth treated as that of A. terrigalensis and not as C. variglandis.

1. The influence of diets having different protein values on the schistosomicidal effect of Ambilhar has been investigated in mice.

2. Mice placed on these diets throughout the period of infection and then treated, reached differently. Low protein diets produced fewer and smaller worms which were more susceptible to the drug.

3. Mice maintained on an adequate diet were shifted to diets of varying protein values a few days before treatment. In these, drug treatment was more satisfactory in animals fed the high protein regimen.

4. Female worms were more affected by drug treatment than the males.

The epidemiology of parasitic infections may be profoundly influenced by infra-specific variations in infectivity for either intermediate or definitive hosts. Such variations will decide the basic ecology of the host-parasite relationship, and variations in virulence and pathogenicity therefore determine different patterns of disease. While some of the evidence of infra-specific variations has been derived from experimental studies, much of it has been recorded by those concerned with investigations of the epidemiology and transmission of parasitic infections and the practical aspects of their control. The unequivocal demonstration of genetic heterogeneity of certain parasites of medical importance has therefore resulted in a better understanding of their epidemiology and, in some cases, is leading to greater precision in attempts to control them.

Two dicrocoeliid trematodes are reported from Ghana. Concinnum ghanensis n.sp. is from the gall bladder and bile duct of the Senegal kingfisher, Halcyon senegalensis (L.), differing from the 14 species recognized in the genus in body shape, the caeca terminating at the vitellarian level or just previtellarian, and the vitellaria being in the form of a band of follicles extending across the body. Dicrocoelium hospes Looss, 1907, is from the bile duct of the Sudan sheep.

1. Infective larvae of S. lupi were collected in Madras from scarabaeid beetles, (the usual intermediate host), from garden lizards and shrews.

2. The structure and relative sizes of the larvae in the 3 kinds of hosts are compared.

3. Infective larvae were given orally to 30 dogs which were autopsied at intervals and the developing worms were recovered. Their growth was measured and some observations were made on their development during the prepatent period which was found to be 121 and 124 days.

(1) The structure of the microfilaria of Brugia (B. patei and B. pahangi) is redescribed and the development of B. patei is followed in the mosquito Aedes togoi for the first 4 days, up to the moult to the second larval stage.

(2) The buccal cavity, the pharynx (or oesophagus), and the pharyngo-intestinal valve of the second stage larva are formed around the pharyngeal thread of the microfilaria. Part of this thread is moulted with the microfilarial cuticle at the moult to the second larval stage.

(3) The intestine of the second stage larva is built up around the Innenkörper of the microfilaria from cells of the nuclear column.

(4) The R cells (G 2—G 4 cells) of the microfilaria and the anal vesicle of the microfilaria continue into the second stage larva and eventually the rectum is formed between them.

(5) The G cell (G 1 cell) does not form part of the gut of the second stage larva but becomes incorporated into the body wall with other cells from the nuclear column.

(6) The subcuticular cells of the microfilaria continue as elongate spindle shaped cells in the cords of the second stage larva.

(7) The significance of these results, which are at variance with earlier descriptions, are discussed and it is concluded that the microfilaria of Brugia is a very much modified first stage nematode larva, adapted to life in the capillaries of the vertebrate host. The microfilaria begins the metamorphosis to the structure of the second larval stage soon after entry into the insect vector.

The life cycle and biology of T. deminutus were studied and investigations were carried out on the site of infection in the host, the female to male ratio, the egg laying capacity of the female worms, the development of the eggs after leaving the host and preliminary observations on the effects of desiccation and low temperatures on the third stage larvae were made.

Eight species of digenetic trematodes, 3 of them new, are reported in fishes from Sierra Leone. Stephanostomum africanum n.sp. (Acanthocolpidae) is from Pseudotolithus senegalensis, S.sierraleonensis n.sp. from Galeoides decadactylus, Pycnadena africana n.sp. (Opistholebetidae) from Lutjanus modestus, Megasolena hysterospina (Manter, 1931) Overstreet, 1969 (Haploporidae) from Chaetodipterus lippei, Aephnidiogenes senegalensis Dollfus, and Capron 1958 (Lepocreadiidae) from Pomadasys jubelini, Lepocreadioides cynoglossi Fischthal and Thomas, 1970, (Lepocreadiidae) from Cynoglossus senegalensis, Lasiotocus cynoglossi Thomas, 1959 (Monorchiidae) from Cynoglossus senegalensis, and Poracanthium ghanensis Fischthal and Thomas, 1970 (Opecoelidae) from Galeoides decadactylus.

Third stage infective juveniles of the genera Oesophagostomum and Ostertagia were found clinging to the abdomens of species of psychodid flies that breed in faeces. It is suggested that these dipterans may be able to carry parasitic nematode larvae from farm to farm.

By clarifying which taxonomic characters are of specific significance and by defining the intra specific limits of individual morphological variations, seventeen species of the genus Anisakis were shown to represent only three distinguishable forms, these being Anisakis simplex (Rudoiphi, 1809 det. Krabbe, 1878), A. typica (Diesing, 1860) and A. physeteris Baylis, 1923. The morphological characters in order of importance for identifying these species are the spicules, the postanal papillae, the form of the ventriculus, the position of the vulva and the form of the lips. These three species were also found to be satisfactory when discussed in geographical and ecological terms.

The four remaining species in the genus, Anisakis dussumierii (van Beneden, 1870), A. alexandri Hsü and Hoeppli, 1933, A. insignis (Diesing, 1851) and A. schupakovi Mozgovoi, 1915 are retained as species inquirendae for lack of sufficient information concerning them.

0·15% of Oesophagostomum larvae fed to laboratory rats became encapsulated in the intestinal mucosa. The juvenile nematodes were able to continue their development when the infected rat tissue was eaten by pigs.

Descriptions of four new tylenchs belonging to different genera are given : (1) Tylenchus (Tylenchus) holochmatus n.sp., (2) Tylenchorhynchus varicaudatus n.sp., (3) Trichotylenchus trilokiae n.sp., (4) Helicotylenchus pteracercus n.sp. The material of the first described species was collected in North India and that of the other new species in South India. Systematic features of new species are fully discussed and compared with those of the related forms.

Detailed descriptions are given of Tylenchorhynchus digitatus and Pratylenchus indicus described by Das (I960) from Hyderabad. The material was collected from type locality but from different hosts. Tylenchorhynchus curvus Williams, 1960, is recorded from India.

Species reported as causing damage to economically important plants in Hyderabad are : Hoplolaimus seinhorsti Luc, 1958, parasitic in cauliflower; Pratylenchus thornei Sher and Allen, 1953, parasitic in maize and Rotylenchulus reniformis Linford and Oliveira, 1940, parasitic in grape vines.

Ichthybothrium ichthybori gen. et sp. nov. (Pseudophyllidea : Ptychobothriidae) is described and figured from specimens collected from the intestine of the African freshwater fish Ichthyborus besse from the White Nile near Khartoum, Sudan. Ichthybothrium and Ptychobothrium show some similarities but can be differentiated by the shape of the scolex and the position of the vitelline follicles. Ptychobothrium cypseluri Rao, 1957 and Plicatobothrium cypseluri Cable and Michaelis, 1967 are congeneric and a new name Plicatobothrium raoi is proposed for the former.

1. 5250 specimens of the common periwinkle, Littorina littorea (L.), from Scalby Rocks on the North Yorkshire coast were examined from October 1966 to November 1967 and data obtained on the size, sex and reproductive condition of the periwinkles and their infections with four species of Digenea, namely Cryptocotyle lingua (Creplin, 1825), Renicola roscovita (Stunkard, 1932), Himasthla leptosoma (Creplin, 1829) and Cercaria lebouri Stunkard, 1932.

2. The normal breeding cycle of uninfected L. littorea and the breeding cycles found in periwinkles infected with larval Digenea are described and discussed. Initial infection takes place mainly when periwinkles are spent after their first breeding season and though later damage to the gonad may prevent reproduction, the breeding potential of the periwinkle population at Scalby Rocks is unlikely to be affected seriously. There was no evidence of sex reversal in uninfected or infected L. littorea and the normal sex ratio is 1:1. The phenomenon of gigantism as a result of digenean infection is discussed with respect to L. littorea.