The histochemical site and distribution of hexokinase, glycogen phosphorylase (GP Rylase), lactate dehydrogenase (LDH) (key enzymes of glycolysis), glucose-6-phosphate dehydrogenase (GPD) and 6-phosphogluconate dehydrogenase (6PGD) (pentose phosphate shunt enzymes), isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and α-ketoglutarate dehydrogenase (α-KDH) (key enzymes of Krebs' cycle), malate synthetase (MS) and isocitrate lyase (IL) (enzymes of glyoxylate shunt) in various tissues of Ganeo tigrinum from hibernating and non-hibernating Rana cyanophlyctis and R. tigrina were studied. Differences in their intensities were revealed. Weak activity of GP Rylase and strong activity of hexokinase in flukes from non-hibernating hosts indicates that they utilize glucose through glycolysis for energy turnover. Intense GP Rylase and weak hexokinase activity in worms from hibernating hosts indicates the utilization of glycogen. Strong activity of IDH, SDH, MDH, α-KGD, MS and IL was demonstrable in the tissues of flukes from non-hibernating hosts, suggesting that Krebs' cycle and glyoxylate shunt, respectively, were operating. Tissues of the fluke from hibernating hosts, on the other hand, displayed positive activity only for SDH and MDH; no activity for MS and IL, the enzymes of glyoxylate shunt, was observed, The activity of the above enzymes was found to be relatively low in worms from hibernating hosts.

Onchocerca raillieti is the only Onchocerca species infecting Sudanese donkeys; it occurs only in the ligamentum nuchae, especially in the lamellar part of the ligament. The morphological features of both uterine and skin microfilariae were determined. Skin microrilariae are shorter than uterine ones and tend to accumulate in the regions of Linea alba and withers of infected donkeys. The possible identity of the vector of this worm in the Sudan is discussed.

Rats acquired a degree of protective immunity to reinfection with Angiostrongylus cantonensis after a single infection with 50 infective larvae. Infected rats resisted the establishment of most challenging larvae and protective immunity increased with subsequent reinfections. Part of the primary infection was lost after a superimposed second and also following a superimposed third infection, but the total size of the concurrent adult worm populations remained the same as that from a primary infection. Worms surviving from the primary infection showed enhanced growth after each reinfection but their fecundity was impaired.

Monanema globulosa (Nematoda: Filarioidea) was recovered from four species of rodents in Kenya, with a prevalence of up to 94% in the striped mouse, Lemniscomys striatus. The adult worms are site-specific to the pulmonary arteries and release sheathed microfilariae that travel via the blood to the skin. Densities of microfilariea in the ears (mf/mg) were five to eight times greater than in any other region of the body and were directly proportional to the number of adult worms present. Highest concentrations of microfilariae in the skin were reached after 100 to 200 days and low numbers persisted in most animals for approximately 500 days.

Third-stage larvae from ticks (Haemaphysalis leachii) injected subcutaneously into jirds migrated widely through the body during early development. Moults occurred twice, after 5 to 10 days and 25 days, and the mean prepatent period was 75 (range 69 to 88) days. A mild eosinophilia developed which peaked after 29 days. Adults in the lungs provoked widespread and intense perivascular cuffing and more localized hypertrophy and fibrosis of the intima in arterioles. Dead adults caused granulomata which obliterated smaller vessels. Microfilariae in the skin elicited no local tissue reaction, but some which invaded the eyes caused a monocyte infiltration of the cornea. It is concluded that the parasite is well adapted to its natural hosts and that it has potential as a rodent model for human onchocerciasis because of the localization of microfilariae in the skin.

Six dogs infected with Dirofilaria immitis and known to develop shock-like reactions after administration of diethylcarbamazine (DEC) were given ivermectin 50μg/kg orally. None of the dogs showed any adverse reaction and subsequently all reacted to DEC 20mg/kg orally.

Another species in the genus Heterocheilus Diesing, 1839, collected from Trichechus senegalensis, is described. It differs from H. tunicatus in possessing elongate cuticular plaques on the body surface in the oesophageal region, a cuticle-lined vestibule between mouth and oesophagus, and triangular interlabial structures. A comparison is made between specimens of H. tunicatus from T. manatus and the specimens from T. inunguis described in a previous paper (Sprent, 1980).

Over 26000 specimens representing five euphausiid species collected, mostly in 1969, in the North-East Atlantic and northern North Sea were examined for parasites. Hysterothylacium sp. larvae were rare, occurring in only two euphausiid samples from inshore localities; the 9 larvae found (3.8 to 12.3 mm long) are described and illustrated. Infection with larval Anisakis simplex was virtually restricted to Thysanoessa spp. and appeared to be discontinuous. Infection was absent to the west of Scotland, and rare to the north of Scotland and at the Faroes. Larval A. simplex was not uncommon in offshore regions of the northern North Sea at depths between 100 and 200 m; the prevalence rate there for individual euphausiid species in individual samples was mostly 0 to 40% but an exceptionally high rate of 78.0% was recorded. Larvae in euphausiids do not become encapsulated but appear to remain active. Experimental observations on the sedimentation rate of A. simplex eggs and hatched larvae in sea water at 10°C are discussed in relation to embryonation and hatching at different temperatures, and depth of the sea. New host records are claimed for larval A. simplex in Nyctiplutnes couchii, and for larval Hysterothylacium sp. in Thysanoessa inermis. No individual euphausiid harboured more than one parasite, either larval nematode or ellobiopsid (see also SMITH, 1981). Morphological and morphometric observations on larval A. simplex from euphausiids are reported elsewhere (SMITH, 1983).

A new genus is proposed for Orneoascaris [ = Amplicaecum] alata (Baylis, 1947) Le Van Hoa, 1960. The new genus is defined and differentiated from Orneoascaris by the posterior position of the vulva and by the wide cervical alae. It is differentiated from Ophidascaris by fewer postcloacal papillae and spicules less than half the length of the ejaculatory duct. From both genera alata differs in the unique form of the lips and in the more extensive U-shaped enlargement of the nucleus of the dorsal oesophageal gland. It is suggested that this species is a specialized form, possibly of neotropical origin.

Four little-known ascaridoid species occurring in crocodilians are discussed. Typhlophorus lamellaris Linstow, 1906 and Hartwichia rousseloti Chabaud& Bain, 1966 are considered to be closely related to Heterocheilus tunicatus Diesing, 1839; Porrocaecum assymmetricum Ortlepp, 1932 is transferred to Trispiculascaris together with T. trispiculascaris Skrjabin, 1916. These three genera are placed in the subfamily Heterocheilinae sensu Sprent (1980) on account of the structure of the oesophago-intestinal junction, the labial pulp and, where known, the male tail. A key to eight genera of Heterocheilinae in crocodilians is provided.