Climate and weather conditions may have substantial effects on the ecology of both parasites and hosts in natural populations. The strength and shape of the effects of weather on parasites and hosts are likely to change as global warming affects local climate. These changes may in turn alter fundamental elements of parasite–host dynamics. We explored the influence of temperature and precipitation on parasite prevalence in a metapopulation of avian hosts in northern Norway. We also investigated if annual change in parasite prevalence was related to winter climate, as described by the North Atlantic Oscillation (NAO). We found that parasite prevalence increased with temperature within-years and decreased slightly with increasing precipitation. We also found that a mild winter (positive winter NAO index) was associated with higher mean parasite prevalence the following year. Our results indicate that both local and large scale weather conditions may affect the proportion of hosts that become infected by parasites in natural populations. Understanding the effect of climate and weather on parasite–host relationships in natural populations is vital in order to predict the full consequence of global warming.

Trichinella spiralis infections may lead to the loss of behavioural dominance among male mice. Reversals of dominance order first appear at the time when newborn larvae are released into the circulation of the host. The duration of dominance reversals bears no relationship to the number of muscle larvae harboured.

The material for this paper was obtained partly at Allahabad and partly at Nagpur from Rana tigrina. In those dissected at Nagpur Centrovitus pentadelphi n.g., n.sp., was found in the duodenum and in the intestine and but once in the oesophagus. This species was also found in the duodenum and intestines of the frogs at Allahabad, but there in addition was obtained once from the stomach and once from the rectum. Ganeo glottoides (Klein, 1905) was found but twice in the intestines of frogs at Allahabad.

The major glycoprotein of the sheath of Litomosoides carinii microfilariae (gp22) was analysed for its amino acid and amino sugar composition. It is rich in proline, glutamine/glutamic acid and glycine and contains (N-acetyl)galactosamine. The N-terminal amino acid sequence was determined up to position 37. It consists of a group of 6 repeats of the pentapeptide sequence methionine-glycine-proline-glutamine-proline with two minor modifications in repeats 3–6, while the first two repeats follow the general pattern more loosely. Identical N-terminal amino acid sequences were found in at least two other sheath polypeptides (33 kDa, 39 kDa). Antisera prepared against 3 overlapping synthetic peptides corresponding to the amino terminus of gp22 recognized different epitopes. They all reacted with identical patterns of sheath polypeptides. The antisera failed to recognize antigens of 4th-stage larvae of L. carinii. In contrast, cross-reacting epitopes were detected in other parasite stages. Antisera reacted with material surrounding embryos and microfilariae in the uterus of females, and caused patchy fluorescence on the sheath of blood-derived and in vitro-released microfilariae.

In spite of the continuing need for new and improved anti-protozoal drugs for use in man, a considerable contraction of industrially based research on anti-protozoal drugs has occurred in recent years. Newton (1983) reviewed the reasons for this decline and presented a compelling argument that fundamental research on the biology of the parasites is essential for the discovery of leads for the development of a new generation of drugs – a rational chemotherapy. The rapid advance in knowledge of the biochemistry of parasitic protozoa which has occurred in recent years has provided a number of potential leads to new drug development and has permitted a greater understanding of the mode of action of many current drugs. The account of these advances which follows is necessarily selective and relates to protozoan parasites of man.

Intrapredatorus barri, a microsporidian parasite of the predator mosquito Culex fuscanus Wiedemann has been shown to be heterosporous. In many features this species has been reported to be similar to Amblyospora trinus, another microsporidian parasite of a different predator mosquito which was thus proposed for reassignation to the genus Intrapredatorus. In this report small subunit rDNA has been sequenced from I. barri and phylogenetic analysis of 42 microsporidia sequences has been performed.Nucleotide sequence data reported in this paper are available in the Gen Bank™ database under the accession number AY013359. The molecular data show that I. barri can not be a member of the genus Amblyospora. Furthermore, the phylogenetic analysis shows, with high confidence, that the Amblyospora spp. sequences in the present study are not monophyletic.

Observations out of doors demonstrated that the viability of embryonated eggs in soil was adversely affected by dryness. This was confirmed in laboratory experiments.

The resistance of embryonated eggs to temperatures below freezing-point was observed both out of doors and in the laboratory.

The rate of development of larvae in the intermediate host was reduced as the temperature fell.

The longevity of the infective larvae appeared to be largely determined by the longevity of the earthworm intermediate host, although they were able to survive for a time when separated from the earthworm's tissues.

The longevity of eggs and larvae under natural conditions and the persistence of infection on a pasture are discussed.

When ring-stage parasites are grown to the late trophozoite stage in vitro, the incorporation of [3H]adenosine into parasite DNA and RNA is in the ratio of ~ 1:1·5 and not 1:4 as expected from direct biochemical analysis of the parasite. A method is described by which large quantities of infected blood can be grown in vitro from the ring to the trophozoite stage thus allowing direct biochemical analysis of parasites grown in vitro. The results of direct biochemical analysis indicated that parasites grown in vitro have similar DNA and protein contents to those grown in vitro but that RNA contents are much less in vitro. Quantitative histochemical studies also indicated a deficiency in RNA in parasites grown in vitro. It is concluded from the evidence of three distinct methods that RNA synthesis is defective during the first asexual cycle in vitro. In the second cycle all three macromolecular biosyntheses studied are reduced when compared to the first so that the actual rate of RNA synthesis is further reduced when compared to that in vitro. It is suggested that the successive decrease in RNA synthesis parallels the reduction in multiplication obtained on subculture of the parasite.

The morphology of the adult blood fluke Schistosoma edwardiense sp.nov. from Hippopotamus amphibius L. is described and compared with that of other species of Schistosoma.

I wish to acknowledge the receipt of a research grant from Makerere University College towards expenses incurred during this work. I should like to thank Captain F. Poppleton, Warden of the Queen Elizabeth National Park, Dr R. M. Laws, Nuffield Unit for Tropical Animal Ecology, and Dr W. M. Longhurst, University of California, for helping me to get specimens from the hippopotami, also Mr L. Rugema, histologist, for sectioning the worms.

Chronic quartan malarial infection has been established in the common marmoset (Callithrix jacchius). Plasniodium brasilianunm from a douroucouli monkey (Aotus trivirgatus) was used to infect splenectomized twin animals, passed to an intact animal, and then to 4 other intact adults, 2 pairs of twins. In 2 of the 4 latter animals there was continuing patency with parasitaemias of ≤0·5% parasitized erythrocytes for 30 weeks. The other 2 had lower initial levels of paraaitaemia; in 1 of these parasitaemias remained low or subpatent. All marmosets developed lymphocytosis. One animal became ill 30 weeks after infection with anaemia, weight loss and mild proteinurea, the other 3 remained well. Histological examination showed minor changes in the kidneys; spleens of infected animals showed marked follicular hyperplasia and phagocytosis of pigment. The livers showed sinusoidal hyper cellularity and pigment deposition and in splenectomized animals, a marked lymphoid follicular hyperplasia in the portal tracts.

Schistosomes are complex parasitic helminths with discrete life-cycle stages, adapted for survival in their mammalian and snail hosts and the external aquatic environment. Recently, we described the fabrication and use of a microarray to investigate gender-specific transcription in Schistosoma japonicum. To address transcriptional differences, 8 gender-associated gene transcripts identified previously by the microarray analysis were selected for further study. First, differential transcription patterns were investigated in 4 developmental stages using real-time PCR. Subsequently, we undertook functional analysis of a subset of 4 transcripts encoding metabolic enzymes, so as to correlate gender-associated transcript levels with enzyme activity in protein extracts from adult worms. The 8 characterized molecules serve as a basis for further investigation of differential gene expression during the schistosome life-cycle and for studying the sexual dimorphism of adult worms. Continual refinement and annotation of the microarray used in the current study should support future work on these aspects.

One of the earliest known Spirochaetes from Lamellibranchs was that briefly described by Certes in 1882 from the crystalline style of the oyster. Certes named the parasite Trypanosoma balbianii. In 1891 the same worker recorded the occurrence of the organism in two species of Tapes, namely T. decussatus and T. pullaster. Laveran and Mesnil in 1901 showed that Tr. balbianii probably belonged to the Spirochaetes. The organism is now known as Spirochaeta balbianii.

The tegumental surface of Schistosoma margrebowiei as viewed by scanning electron microscopy is described. Both spined and unspined tubercles were found on the dorsal and dorso-lateral surfaces of sexually mature (in copula) male worms. Unpaired males lacked spined tubercles and the development of the spines is considered to occur only when worms are in copula. The females lack tubercles. The importance of tubercle structure in the identification of schistosome species and the effect of sexual maturity on their development is discussed.

This communication is the first of a series dealing with Mallophaga from Australian marsupials. We had hoped to prepare a single monographic work on the Family Boopidae, but the carrying out of this plan has been prevented by a variety of causes, and we think it advisable to publish piecemeal the notes and descriptions that we have accumulated during the last six years. There has of late years been a recrudescence of interest in the Mallophaga, and a considerable number of students are now investigating the group. Little has been published upon the very distinct family which is characteristic of Australian marsupials, and it is important that students of the group should have diagnoses of the family, sub-families, and genera, based upon an ample material, which includes all the known species, with a single exception, and more than an equal number of undescribed new forms. Such a material is at our disposal. Apart from our own collections, Mr A. S. Le Souëf has very kindly transferred to us all his Mallophaga from marsupials, including his types.

The behaviour of cercariae was recorded on video at 10, 20 and 30 °C and a combination of population and individual behavioural patterns studied. Initially cercarial populations were extremely active, individuals alternating between swimming and sinking behaviour. As they aged the percentage sinking and resting increased resulting in the establishment of a vertical distribution in the water column. An increased environmental temperature reduced the active life-span of the parasites. Over time cercarial swimming rates declined. Swimming rates increased with environmental temperature and as a result of a shadow stimulus. As cercariae aged, the duration of swimming events decreased. Post-stimulation swimming periods were significantly longer than pre-stimulation periods. Pre- and post-stimulation swimming distances also declined with age. Post-stimulation swimming distances were significantly longer than pre-stimulation distances. The sinking rates of cercariae decreased with age while sinking periods and distances increased. Data for proportional time spent swimming and the ratio of sinking to swimming events indicated that as cercariae aged, less time was spent swimming. The frequency of swimming/sinking events declined with age. The implications of this behaviour for dispersal and transmission are discussed.

Neonatal hamsters were exposed to varying doses of Necator americanus larvae and changes in the stability of the resulting worm burdens were monitored over a period of 25 weeks. No change in worm burdens was evident for the first 5 weeks of infection, irrespective of the infection intensity, but the more heavily infected groups subsequently lost worms in a density-dependent manner. Male and female hamsters lost comparable proportions of their established parasite burdens indicating that there was no host sex-linked difference in this respect. By week 15 infections had stabilized and the residual worm burdens, usually a maximum of 30 worms survived for a considerably longer period of time. Initially the percentage of male worms varied from 45% to 50% but as infection progressed male worms comprised a significantly increasing proportion of the total worm burden. By week 25 the percentage of male worms was usually in excess of 60%. The growth of infected animals was not severely affected by N. americanus, even when heavy worm burdens established initially, but a significant effect was detected particularly in week 5, prior to worm loss, when the adult worms would have been feeding on intestinal tissues and causing blood loss for a period of about 2 weeks. The most severe depression in the packed cell volume was also recorded in week 5, indicating that anaemia had been initiated in infected hamsters. Whilst, the regulation of parasite burdens in weeks 5–10 post-infection may have resulted from host immunity, the persistence of the residual worm burdens, the marked density-dependent anaemia and the subtle effect on host weight, all reflected well-documented aspects of chronic human necatoriasis.

The inner cyst tissue development is anteriad and centripetal. The cells produce lamellar extensions which assume parallel alignment. The first contact points (approximately 4 days post-infection) establish heptalaminar (gap) junctions. Lamellar attenuation results in a decreased intercellular space, and at 5–6 days pentalaminar junctions (with fused outer plasmalemma leaflets to give an electron-dense, approximately 3 nm wide O–O line) occur. This is the first maturation (Ml) stage. The O–O lines are permeable to lanthanum, and evidence of their possible transformation from heptalaminar junctions is presented. Continued lamellar attenuation, associated with scolex retraction and subsequent growth, results in cytoplasmic occlusion and contact between the inner leaflets of the same lamella. The resultant electron-dense I–I line is approximately 3 nm wide; the O–O line is now less electron-dense and thinner (approximately 2 nm). This final maturation (M2) stage, resembling vertebrate myelin, occurs over limited areas; closely adjacent regions either remaining at the M1 stage, or not displaying junctional complexes. Since in vivo and in vitro excystment can occur before the M2 stage, the inner cyst tissue is not considered to be protective against the definitive host. That the tissue may function in limiting nutrient flow, thus regulating the size of the presumptive adult, is discussed.

Demodex carolliae, a parasite of the bat Carollia perspicillata, is described for all stages of its life cycle. The sequences and adaptive features of this life cycle are detailed. Some information is presented on the population structure and the pathogenicity of this species.

This research was supported in part by Grant W83–1 to Dr F. Lukoschus from the Netherlands Foundation for the Advancement of Tropical Research (WOTRO).

We have cloned a cDNA encoding a novel antigen from a Sarcoptes scabiei (Acari) cDNA library by immunoscreening with sera from S. scabiei-infected dogs. The antigen is encoded by a 2157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39·7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62 S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

1. The means of attachment of the mite Myocoptes musculinus to the hair of the host, the mouse, and the sites where it is located are given.

2. Normal and skin infected with M. musculinus of young (6–8 weeks) and adult (6 months) mice is treated with colchicine and examined histologically.

3. Infected skin shows a mitotic count of approximately four times that of normal skin in the adult; there is no appreciable difference in the young.

4. Acaricides used to control the mite were benzene hexachloride (0·015%), dieldrin (0·015%), arsenic and sulphur mixture (0·018% arsenic), piperonyl butoxide (5%) and dimethylphthalate (100%); the latter being the most efficacious.

5. It is established that the drugs had no effect on the rate of division of the cells of the malpighian layer of the skin.

6. The number of Myobia present increases as the Myocoptes are killed unless dimethylphthalate, an oily liquid, is used at intervals.

7. Diet in conjunction with signs of mange is discussed.

8. Carriers of M. musculinus are given.

I wish to thank Cooper McDougall for supplying the materials used in dipping and swabbing, and the Infestation Control Laboratory of the Ministry of Agriculture for supplying me with a number of specimens of wild mice from different parts of the country. I am also grateful to the Council of the Royal Free Hospital School of Medicine for facilities for carrying out the work; and to Dr A. M. Hughes for her helpful guidance at all stages of the work and especially for reading the paper.