Removal of the sheath of the ensheathed infective juvenile of Trichostrongylus colubriformis prevents capture by the nematophagous fungus Arthrobotrys oligospora. Exposure of the trap hyphae to a variety of saccharides, which may block a recognition system based on lectin/carbohydrate binding, failed to prevent capture but some saccharides did inhibit penetration and invasion by the fungus. Capture and penetration thus appear to be two distinct processes with capture being less specific than penetration. Carbohydrate residues were absent from the outer surface of the cuticle and the sheath but were present on the inner surface of the sheath. The limited accessibility of these lectin-binding sites may explain the slow process of infection of the infective juvenile by the fungus. The sheath does not protect the infective juvenile against attack by this nematophagous fungus.

This review highlights studies conducted in murine models to evaluate the efficacy of compounds targeting Heat shock protein (Hsp) 90 of malaria. Both advances achieved and limitations that exist are highlighted.

During an examination of fishes for the parasitic crustaceans, fourteen specimens of Argulus belonging to two different species, viz. A. indicus Weber, 1892 (eight specimens) and A. siamensis Wilson, 1926 (six specimens) were collected from the fish, Ophiocephalus marulius Hamilton, taken from a canal in the environs of the village Champahati, District 24 Parganas, West Bengal. Out of seven fishes so obtained only three were found to be infected with the copepod parasites. While examining these copepods, the attention of the writer was drawn to a viviparous monogenetic trematode infecting only one species of Argulus, viz. A. indicus. It was rather unfortunate that the piscine host could not be examined at that stage for the helminthic infection. About one hundred specimens of this trematode were collected from the ventral surfaces of the copepods.

In 1941 work was started in North America with a view to introducing into South Africa parasite species which might act as factors in the control of the insect pest, Loxostege frustalis Zell. (Pyraustidae), which destroys large areas of Karroo bush (Pentzia incana), an important sheep-fodder plant in South Africa (Taylor, 1940). Several nearly related species of moths occur in North America, one of them being Loxostege sticticalia L., a serious pest of sugar-beet in the Great Plains region. A number of parasite species have been recorded from this host both in America and Europe (Pepper & Hastings, 1941), and it was thought that several of these species occurring in North America might be suitable for introduction into South Africa after their hiolocv and life histories had been investigated.

Simple sequence repeat markers have played an important role in elucidating the epidemiology of human and animal cryptosporidiosis. The drawback of sequence length polymorphisms is that nucleotide substitutions remain undetected. As some laboratories have opted for using length polymorphisms, while others have relied on sequencing, there is a need to compare both methods. We used a diversified set of unique length polymorphisms and matching nucleotide sequences to assess the ability of each genotyping protocol to discern clusters of related Cryptosporidium parvum isolates. We found a weak correlation between the two distance measures for individual markers. This analysis was extended to four-locus genotypes based on sequence length data or concatenated sequences from the same loci. We interrogated these data to assess whether one would reach the same conclusions regardless of the genotyping method. Clusters of isolates generated with the concatenated sequences were not observed with amplicon length, indicating that inferences on the structure of a Cryptosporidium population depend on the genotyping method. Moreover, isolate clusters derived from concatenated sequences were dependent on the algorithm used to calculate distances. These results emphasize the need for harmonizing genotyping tools, not only by selecting informative markers, but also by standardizing the entire genotyping method.

The present study shows an in vivo role for interleukin-2 in the formation of hepatic granulomatous inflammation in murine Schistosoma japonicum infection. Mice which had been administered an inhibitor to interleukin-2 function during acute infection were noted to have reduced cell-mediated immune responses to ConA and S. japonicum soluble egg antigen (SEA). Lymphoid tissue from these treated mice also have reduced numbers of cells which could be activated by ConA to produce interleukin-2 mRNA as shown by in situ hybridization studies. Mice with less activated lymphocytes had, on the average, a 70% reduction in the granulomatous inflammation surrounding eggs deposited in hepatic tissues of acutely infected mice. The data demonstrate that IL-2 is a key factor in the generation of granulomatous inflammation in S. japonicum infection and suggest that a potential anti-pathology vaccine could be generated based on limiting the presence of IL-2 generated during acute infection.

Angiostrongylus cantonensis (rat lungworm) is a tropical and subtropical parasitic nematode, with infections in humans causing angiostrongyliasis (rat lungworm disease), characterized by eosinophilic meningitis. Hawaii has been identified as a global hotspot of infection, with recent reports of high infection rates in humans, as well as rat definitive and snail intermediate hosts. This study investigated variation in A. cantonensis infection, both prevalence and intensity, in wild populations of two species of rats (Rattus exulans and R. rattus) and one species of snail (Parmarion martensi). An overall infection prevalence of 86.2% was observed in P. martensi and 63.8% in rats, with R. exulans (77.4%) greater than R. rattus (47.6%). We found infections to vary with environmental and host-related factors. Body mass was a strong predictor of infection in all three species, with different patterns seen between sexes and species of rats. Infection prevalence and intensity for R. exulans were high in May 2018 and again in February 2019, but generally lower and more variable during the intervening months. Information on sources of variability of infection in wild host populations will be a crucial component in predicting the effectiveness of future disease surveillance or targeted management strategies.

1. A new variety of the trematode Harmostomum opisthotrias is reported from the North American opossum.

2. Body proportions in this genus are more constant than linear dimensions and are, therefore, considered more desirable as a basis for taxonomic distinctions.

3. The occurrence of this parasite in a host with a range as limited and a phylogenetic position as critical as that of the opossums suggests the possibility of valuable information to be obtained through host-parasite relationship studies in this group. Investigators who are working with this material should keep the problem in mind.

1. Trypanblau injected subcutaneously into dogs a day before or a day after they have been inoculated with blood containing Piroplasma canis effectually prevents the development of piroplasmosis by destroying the parasites at the onset of infection.

2. Trypanblau given by the mouth is ineffective, since it exerts no apparent influence either upon the parasite or upon the course of the disease.

3. Tryparosan, when injected subcutaneously or when given by the mouth, has no effect upon the parasite and is ineffective as a remedy against piroplasmosis in the dog.

Species composition of wild reservoir hosts can influence the transmission and maintenance of multi-host vector borne pathogens. The ‘pace of life’ hypothesis proposes that the life history strategy of reservoir hosts can influence pathogen transmission of vector borne generalist pathogens. We use empirical data to parameterize a mathematical model that investigates the impacts of host life history traits on vector transmission dynamics of the vector-borne multi-host parasite Trypanosoma cruzi in habitats characterized by different degrees of deforestation and varying host community structure. The model considers susceptible and infected vector and host populations. When comparing the proportion of vectors infected with T. cruzi predicted by the model with empirical data, we found a trend of increasing vector infection as anthropogenic landscape disturbance increases for both data and model output. The model's vector infection rates were significantly lower than empirical results, but when incorporating host congenital transmission in the model, vector infection approaches field data. We conclude that intervened habitats associated with r-selected host species communities predict higher proportions of infected vectors.

By transferring Schistosoma mansoni (12 to 14-day-old worms) from one host into the peritoneal cavity of a host of a different species, it was possible to demonstrate that worms grown in rats, hamsters, Mastomys natalensis and Cebus monkeys were rejected by recipient animals previously immunized against red blood cells of the donor hosts. These results suggest that host-like antigens are acquired by S. mansoni in all hosts. The transfer of worms into the peritoneal cavity has proved to be a simple and convenient method for studying the presence of host antigens in S. mansoni.

We compared lizard endoparasite assemblages between the Atlantic Forest and naturally isolated forest enclaves to test the ecological release hypothesis, which predicts that host specificity should be lower (large niche breadth) and parasite abundance should be greater for parasites from isolated forest enclaves (poor assemblages) than for parasites from the coastal Atlantic Forest (rich assemblages). Parasite richness per specimen showed no difference between the isolated and non-isolated areas. Parasite abundance did not differ between the isolated and non-isolated areas but showed a positive relationship with parasite richness considering all areas (isolated and non-isolated). Furthermore, host specificity was positively related to parasite richness. Considering that host specificity is inversely proportional to the host range infected by a parasite, our results indicate that in assemblages with greater parasite richness, parasites tend to infect a smaller range of hosts than do those in simple assemblages. In summary, our study partially supports the ecological release hypothesis: in assemblages with greater parasite richness, lizard parasites from Atlantic Forest are able to increase their parasite abundance (per host), possibly through facilitated infection; however, the amplitude of infected hosts only expands in poor assemblages (lower parasite richness).

Bovine babesiosis is the most important protozoan disease transmitted by ticks. In Plasmodium falciparum, another Apicomplexa protozoan, the interaction of rhoptry neck protein 2 (RON2) with apical membrane antigen-1 (AMA-1) has been described to have a key role in the invasion process. To date, RON2 has not been described in Babesia bigemina, the causal agent of bovine babesiosis in the Americas. In this work, we found a ron2 gene in the B. bigemina genome. RON2 encodes a protein that is 1351 amino acids long, has an identity of 64% (98% coverage) with RON2 of B. bovis and contains the CLAG domain, a conserved domain in Apicomplexa. B. bigemina ron2 is a single copy gene and it is transcribed and expressed in blood stages as determined by RT-PCR, Western blot, and confocal microscopy. Serum samples from B. bigemina-infected bovines were screened for the presence of RON2-specific antibodies, showing the recognition of conserved B-cell epitopes. Importantly, in vitro neutralization assays showed an inhibitory effect of RON2-specific antibodies on the red blood cell invasion by B. bigemina. Therefore, RON2 is a novel antigen in B. bigemina and contains conserved B-cell epitopes, which induce antibodies that inhibit merozoite invasion.

Avian malaria is a mosquito-borne disease caused by Plasmodium spp. protozoa. Although these parasites have been extensively studied in North America and Eurasia, knowledge on the diversity of Plasmodium, its vectors and avian hosts in Africa is scarce. In this study, we report on natural malarial infections in free-ranging sparrows (Passer domesticus) sampled at Giza Governorate, Egypt. Parasites were morphologically characterized as Plasmodium cathemerium based on the examination of thin blood smears from the avian host. Sequencing a fragment of the mitochondrial cytochrome b gene showed that the parasite corresponded to lineage PADOM02. Phylogenetic analysis showed that this parasite is closely related to the lineages SERAU01 and PADOM09, both of which are attributed to P. cathemerium. Experimental infection of Culex pipiens complex was successful, with ookinetes first detected at 1-day post infection (dpi), oocysts at 4 dpi and sporozoites at 6 dpi. The massive infection of the salivary glands by sporozoites corroborates that Cx. pipiens complex is a competent vector of PADOM02. Our findings confirm that Plasmodium lineage PADOM02 infects sparrows in urban areas along the Nile River, Egypt, and corroborate that Cx. pipiens complex is a highly competent vector for these parasites. Furthermore, our results demonstrate that this lineage corresponds to the morphospecies P. cathemerium and not P. relictum as previously believed.

Host invasion and tissue migration of several helminths have been linked to expression and release of parasite-derived proteinases. The plerocercoid of the cestode Proteocephalus ambloplitis can migrate into the visceral organs or, in the case of bass, from them into the intestinal tract of the same individual fish. It does this within a few hours, aided by secretion of a substance from its apical gland. Proteinase activity in this plerocercoid, obtained from the host liver, was defined by pH optimum, by substrate and inhibitor specificity, and by electrophoretic and chromatographic techniques. Homogenates of plerocercoid contained a metalloproteinase exhibiting a molecular weight of 30000 determined by gelatin substrate gel electrophoresis. Peak activity of this proteolytic enzyme in gel filtration fractions when azocoll was used as substrate then corresponded to a molecular weight of 31500. The proteinase showed collagenolytic, haemoglobinolytic and slight elastinolytic activity, and it had a pH optimum at 9·0. Enzyme activity could be inhibited by various chelating agents. The metalloproteinase identified in this study constitutes the only enzyme class present in this larval stage of P. ambloplitis. We suggest that the plerocercoid's metalloproteinase is the substance secreted from the apical organ, necessary for the previously recognized tissue migration phase. This enzyme might also have a nutritional function.