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The occurrence of the louse Hoplopleura pacifica on Rattus norvegicus from Barcelona is reported. The rats infested were caught in two different biotopes: the sewer system and the port.

We have studied the development of Schistosoma mansoni in two natural hosts, Rattus rattus and Rattus norvegicus, and in two laboratory hosts, the white Mouse and the white Rat. The study of survival shows that the percentage of cercariae recovered as adult worms four weeks after exposure is 31% in R. rattus, 27% in the white Mouse, 14% in the laboratory Rat and 12% in R. norvegicus. Twenty weeks after exposure, 62% of the Schistosomes which were present four weeks after exposure are still alive in the Mouse, 48% in R. rattus, 8% in R. norvegicus and 5% in the laboratory Rat. The study of growth shows that the average size of males eight weeks after exposure is 7 mm in the Mouse, 5.1 mm in R. rattus, 2.9 mm in the white Rat and 2.6 mm in R. norvegicus. The study of egg production shows that S. mansoni lays eggs in the four Rodents; however only mice and R. rattus eliminate fertile eggs containing infectious miracidia of S. mansoni; in R. norvegicus, as in the white Rat, the eggs of S. mansoni are not fertile and are never eliminated by the host. These results demonstrate that susceptibility is not always associated with permissivity and there is a great difference between the two natural hosts; R. norvegicus accepts S. mansoni but does not allow its transmission; R. rattus which is more favourable to growth and reproduction of S. mansoni, allows the transit and exit of fertile eggs. These experimental data indicate that R. rattus is able to play a part in the dynamics of the guadeloupean schistosomiasis focus while R. norvegicus is unable to contribute to the circulation of S. mansoni and is a decoy host for the parasite.

Leptospiroses in Morocco have been studied from 1979 to 1981. In man, L. icterohaemorrhagiae is the most frequently diagnosed serotype. The highest incidence of positive diagnoses is found in Fès-Meknès area. Leptospirosis is a severe disease: 1 out of 3 patients is hospitalized in Intensive Care Unit. Rat is an essential carrier of germs in Casablanca.

The "miracidial chaetotaxic index" of a human strain of Schistosoma mansoni from West-Africa displays an abrupt decrease following three first transmissions Biomphalaria pfeifferi, white mouse. Then it increases gradually up to a new balance. The value of the index permits to estimate the human or murine characteristic of the natural infections in Guadeloupe. According to stations the index of miracidia issued from rats is widely different. Stations where both rat and man are infected show strong differences from a station where infection seems exclusively murine (Grand-Etang). Results agree with these concerning cercariae. Possibility of intervention of murine strains infecting man in Guadeloupe and apt to cause an especially severe bilharziasis is called up.

A study of S. mansoni schistosomiasis in R. rattus and R. norvegicus naturally infected in the Guadeloupean focus confirms the results previously obtained with experimental infections in the Rodents. The number of Schistosomes varies from 1 to 600 (on average: 119 +/- 73) in R. rattus and from 1 to 56 (on average: 21 +/- 14) in R. norvegicus. The sex-ratio for all Schistosomes counted in wild Rats is 1.08 for 51.89 +/- 1.78% males and 48.11 +/- 1.78% females; the difference is not significant. The average size of males is greater in R. rattus (5.48 +/- 0.38 mm) than in R. norvegicus (3.73 +/- 0.28 mm); these values are slightly higher than those obtained with Schistosomes collected eight weeks after experimental exposure of Rats.

Thirteen species of trichostronglyloid nematodes have so far been recorded from wild birds and mammals in Israel and surrounding territories. Three species were found in birds: Amidostomum fulicae (Rudolphi, 1819) in Fulica atra L., 1758, A. acutum (Lundahl, 1848) in Anas crecca L., 1758 AND Amidostomum sp. in Ceryle rudis L., 1758. Ten species, 3 of which are new, were found in small mammals: Trichostrongylus colubriformis (Giles, 1892) in Hystrix indica Kerr, 1792; Tenorastrongylus josephi n. sp. in Mus musculus L., 1758; Nippostrongylus brasiliensis (Travassos, 1914) in Rattus norvegicus Berk, 1796 and Rattus rattus L., 1758; Nippostrongylus witenbergi Greenberg, 1972, in Nesokia indica Gray et Hardw., 1832; Heligmonina nevoi n. sp. in Spalax ehrenbergi, Nehring, 1898; Boreostrongylus seurati (Travassos et Darriba, 1929) in Gerbillus allenbyi Thomas, 1918, G. pyramidum Geoffrey, 1825, G. (Dipodillus) dasyurus, Meriones sacramenti Thomas, 1922 and M. tristrami Thomas, 1892; Boreostrongylus minutus (Dujardin, 1845) in Microtus guentheri Danford et Alsen, 1880; Heligmosomoides polygyrus polygyrus (Dujardin, 1845) in Apodemus mystacinus Danf. et Alst., 1877 and A. sylvaticus L., 1758; Suncinema witenbergi n. sp. in Crocidura russula Herm., 1780. Ecologic and zoogeographic relationships are discussed.

Description of a new species of Oxyurid: Syphacia (Syphatineria) callosciuri n. sp. parasite of a Sciurid rodent Callosciuris caniceps in Malaysia. In rodents belonging to the genus Callosciurus in Malaysia two species: S callosciuri n. sp. and S. owyangi Quentin, 1975, show morphological characteristics which are intermediate between the primitive Syphacia and two different lines of species parasite of recent rodents. These observations appear to indicate that the adaptation of Syphacia of Sciurids to the modern rodents has occured in South-East Asia.

A description is given of the blood stages of a new subspecies of Plasmodium vinckei in the blood of naturally infected thicket rats (Thamnomys rutilans) from Nigeria and experimentally infected mice. Sporogony was obtained at 25 degrees C in Anopheles stephensi A. quadrimaculatus and A.l. atroparvus, but sporozoites in the salivary glands of the mosquitoes were never infective. The new parasite is differentiated from 7 other species of malaria parasites of African rodents principally on the morphology of the erythrocytic stages. It is designated as a subspecies of P. vinckei (P.v. brucechwatti subsp. nov.) because of the (i) zoogeography, (ii) morphology of sporogonic stages and (iii) forms isoenzymes of blood stages.

The study of the rate of contamination of B. glabrata and the cercarial densities of S. mansoni in the chanels of Beaugendre valley (Guadeloupe, French West Indies) concentrates attention on the focalisation of the sites with high risk of contamination. This focalization of the sites of transmission is directly related to the regular deposition of human faeces. A small number of contamined people is enough to maintain high cercarial densities (230 c/1). In the chanel studied, the role of the rat in the transmission of the parasite seems less important than that of the Man. The infection of the rats during consumption of snails can be foreseen.