Six to nine horses per month (total of 94 in a year) were examined for stomach worms in the Settat region of Morocco. All the animals were infected by at least one helminth species. Habronema muscae occurred in 95–8%, H. majits in 75.6% and Trichostrongylus axeiin 80.9% of horses. Polyparasitism was observed in 93.6% of horses. Both for Habronema spp. and T. axei the peak worm burden was observed in November and minimum in June. The infection pattern Habronema spp. was directly related to the period of activity of fly vectors.

Onchocerca tarsicola is a subcutaneous filariid of the red deer living on the tendons of the radial-carpal and tibial-tarsal joints. Its micronfilariae concentrate mainly in the external ears. The extrinsic cycle of this parasite was investigated. In a hyperendemic area wild-caught Odagmia ornata were dissected, as well as samples which had fed on a tame deer and been kept in the laboratory after the infecting blood-meal. About 3 to 5% of the flies were infected with larval stages of Onchocerca tarsicola. More than 40% of Odagmia ornata induced to feed on the ears of the deer became infected and about 30% of the flies which survived more than 18 days contained third-stage larvae. The larval development in the vector is described. Prosimulium nigripes appears to be a second natural vector of Onchocerca tarsicola. Observations concerning the potential vectors of O. Jlexuosa, O. tubingensis and Cutifilaria wenki living in red deer are discussed.

Experimental infections were established with Diphyllobothrium sp. plerocercoids obtained from Salmo gairdneri. a fish introduced at the beginning of the 1900s in the lake region of Chile. These permitted us to obtain adult parasites in Larus dominicanus and Canis familiaris.

The histological features of the plerocercoids, their relation to the host, adult pattern and susceptibility of hosts allowed us to determine the presence of Diphyllobothrium dendriticum (Nitzch) for the first time in South America in the lacustrine region of southern Chile.

It is believed that this cestode was introduced to this ecosystem by infected persons travelling from North America or Europe or, alternatively, brought by migratory birds, e.g., Sterna hirundo, S. paradisea or Larus pipixcan on their winter visits to South America.

Fly load of Onchocerca volvulus microfilariae and their early development in Simulium ochraceum were examined at intervals of 10, 30 and 60 min after ingestion and then hourly up to 72 hours. Many microfilariae ingested were damaged by the cibarial armature of the vector, limiting the fly load, but some of these damaged microfilariae were able to penetrate the gut before they died. Thus, the mean number of the living parasites per fly in the head and thorax decreased gradually with elapse of time after ingestion. The parasites ingested by S. ochraceum did not develop beyond the microfilarial stages during the first 24 hours; thereafter only thoracic forms (lst-stage larvae) were found to be alive. The high mortality of the infected fly might be caused by the high intakes of microfilariae and also by normal and/or partly wounded microfilariae invading various organs. The numbers of microfilaria ingested from different biting sites were usually high in comparison with the densities observed in each site; this indicates that the microfilariae might be attracted by the biting females.

Sera from 36 slaughtered camels with proven hydatid disease, from 46 camels found to be free of hydatidosis at post-mortem meat inspection, and from 26 animals with confirmed caprine heartwater, bovine trypanosomiasis and cysticercosis were examined. The indirect haemagglutination was found to be the most sensitive but least specific of the three tests. Ouchterlony's double diffusion (DD) test was specific and fairly sensitive. Although the countercurrent immunoelectrophoresis was as specific as DD, it was the least sensitive of the three serological tests.

All three serological tests were always positive in camels with hydatid cyst infection affecting both the liver and the lung. A combination of indirect haemagglutination and Ouchterlony's double diffusion tests could be useful for diagnosing hydatidosis in camels and probably other animals.

Experiments were carried out to investigate if sera of animal species other than dog are chemotactically active for infective larvae of Ancyclostoma caninum. Those sera were also found to contain such a factor(s), although the larvae were attracted significantly better by dog serum. How this chemotaxis might be applied to the in vivo situation, when infective A. caninum larvae penetrate the skin of dogs, is discussed.

The metacestodes of Taenia crassiceps removed from a stock infection of Sprague Dawley rats were injected into seven inbred and one outbred strain of rats. The results showed that over-all female rats are more susceptible to the infection than male rats. Only one strain of rat, the Lewis male rats, was found to be resistant to the infection. There was no significant difference in the volume of metacestodes recovered from the male and female rats. The sizes of the metacestodes, after two passages through the rats, were compared to those of the original mouse strain and it was found that metacestodes from two strains of rats were significantly smaller. The antigenic expression of the metacestodes from the different strains of rats was compared and some variation in the antigenicity was observed.

Two types of neurosecretory cells (NSC), large a cells and small β cells were detected on the basis of their size and characteristics as shown by aldehyde fuchsin and chrome haematoxylin-phloxin staining. A histochemical survey of the neurosecretory material indicates that it is a glycoprotein. Phosphatases and esterases present in NSC probably help in the transfer of metabolites and their hydrolysis and in the control of secretory material produced in a NSC, while SDH provides the necessary energy for the synthetic activity of the latter. The role of neurosecretion in governing the reproduction of this parasite is discussed.

The critical-point-dried specimens of Gastrothylax crumenifer (Creplin, 1847) Poirier, 1883 and Paramphistomum epiclitum Fischoeder, 1904, both recovered from the rumen of sheep, were studied by scanning electron microscopy at magnifications ranging from 10 to 10,000 x to reveal the structural differences of the tegument between the two species.

In G. crumenifer, both dorsal and ventral surfaces have tubercle-like tegumental elevations, devoid of spines. A row of prominent, regularly arranged, button-like protuberances encircle the rim of mouth. It is suggested that these are sensory in nature. The lining of the buccal tube also bears papillae, some of which appear balloon-like. The tegument near the outer acetabular rim is thrown into prominent ridges bearing groups of six to eight small papilla-like elevations. Towards the interior of the acetabular cavity this pattern merges into one with stout, finger-like projections with groups of papillae at their blunt tips. From their structure, these projections appear to aid strong anchorage to the host's surface and the papillae to be secretory.

P. epiclitum has a similar tuberculated pattern on the dorsal and ventral surfaces. In the oral region, the tegument has some irregular, patch-like elevated areas. The acetabular surface is thrown into a pattern of deep folds and craters.