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Natural Schistosoma mansoni infection in wild rats from Guadeloupe: parasitological and immunological aspects.

Rattus rattus is the predominant rodent in the mangrove area of Guadeloupe. Between 1990 and 1991 we found 73 R. rattus and five R. norvegicus. Among the infected rats with Schistosoma mansoni, 59% for R. rattus and 80% for R. norvegicus, the comparison of the median of the worm load was not statistically different. Both species of infected rats showed adult worms and eggs in the lungs and 20% of them showed, at the same time, two and even three generations of worms. Neither adults nor eggs were seen in the intestinal wall or stools of R. norvegicus, instead R. rattus had eggs in the liver, in the intestinal wall and the stools. Therefore, R. norvegicus gets infection as well as R. rattus, but does not participate in the transmission of the schistosomiasis. In order to elucidate this difference, we looked at the humoral recognition of these two rats, to the molecular antigens of the three stages of the parasite: cercaria, adult worm (AWA) and egg (SEA). In general, R. norvegicus recognized cercarial antigens more frequently than R. rattus, 73, 81 and 172 kDa being statistically different. Regarding AWA, molecules 82, 86, 117 and 150 kDa were recognized more often by R. rattus as compared to R. norvegicus. The reverse was true for the 18, 33 and 61 kDa. Only the differences between 61 and 150 kDa molecules were statistically significant. With respect to SEA, R. norvegicus recognized more 28, 45, 47, 49, 64 and 92 kDa molecules than R. rattus, but the latter recognized the 140 kDa molecules of SEA to a higher degree (95 and 140 kDa were significantly different). It is plausible that the immune response to cercarial invasion is more effective in R. norvegicus in allowing the parasites to reach adulthood, but it does not let them live in the mesenteric veins and therefore to lay their eggs in the intestinal wall and feces.

Animals↗

Companion animal parasitology: a clinical perspective.

In recent years there have been many changes to the ways that clinical veterinary science is conducted and nowhere is this more evident than in companion animal practice. Veterinarians working with pet dogs and cats are facing new challenges associated with the emergence and re-emergence of parasitic diseases. Some, such as Neospora caninum, have been recently recognised; others like Giardia and Cryptosporidium have been reported with increasing frequency, in part as a result of laboratory tests with improved sensitivity and specificity. In many regions, the emergence of parasitic diseases has been a consequence of pet travel and exotic diseases pose a unique diagnostic challenge for the veterinarian, as the index of suspicion for these conditions may be absent. The ranges of certain vector-borne diseases such as babesiosis, hepatozoonosis, ehrlichiosis, leishmaniasis and dirofilariasis are extending due to ecological and climatic changes and enhanced by animals with subclinical infection returning home from endemic areas. In companion animal practice, veterinarians have the additional responsibility of providing accurate information about the zoonotic transmission of parasite infections from pets, especially to those most vulnerable such as children, the elderly and the immunocompromised. Effective education is vital to allay public concerns and promote responsible pet ownership.

Animals↗

Physiology, pharmacology and parasitology.

The developing resistance to current chemical classes of broad-spectrum anthelmintics and insecticides presents an undeniable threat to the long-term viability of the animal health industry. Alternative treatment strategies including vaccines, biological control and breeding of parasite-resistant animals are unlikely to be widely available in the near future and even then they will be integrated with chemotherapy. The significant cost of research and development of new therapeutics for food-producing animals, together with the small market share of animal health products, particularly in Australia and New Zealand, is a positive disincentive for drug development. The chemical actives that are currently available are all that we are likely to have for the foreseeable future and they must be used more efficiently. Understanding the pharmacokinetic behaviour of antiparasitics and recognising the potential for the animal's physiological characteristics to assist drug action is crucial. Careful administration, coupled with a reduction of feed intake before oral anthelmintic treatment, maximises drug availability and therefore increases efficacy of the benzimidazole and ivermectin compounds. This is a cost-effective option that can be employed immediately, which not only increases efficacy of "older" compounds but will be instrumental in prolonging the useful life of the newer drugs. Taking care to apply topical insecticide formulations directly along the backline immediately after shearing will maximise even diffusion of active around the sheep flanks to contact lice inhabiting sites remote from the point of drug application. The use of "intelligent" formulation and delivery of existing compounds, based on knowledge of host physiological and pharmacological responses, holds the key to effective antiparasitic treatment.

Animals↗

Urinary schistosomiasis in schoolchildren on Zanzibar Island (Unguja), Tanzania: a parasitological survey supplemented with questionnaires.

The distribution of urinary schistosomiasis in schoolchildren on Zanzibar Island (Unguja) was surveyed in May 2001 to test a potential correlation with the distribution of snail species of the Bulinus africanus group and to record contemporary baseline epidemiological data. Quasi-random samples of 40 schoolchildren of mixed sexes were selected from each of 10 schools. Schistosoma haematobium infections were detected upon the basis of micro-haematuria with subsequent confirmation by microscopy examination for schistosome eggs. At the time of urine collection, each child was interviewed with a suite of 12 questions prepared as a standardized questionnaire. Total prevalence of urinary schistosomiasis (known locally as kichocho) was 12% although schistosome infections were absent in 5 schools. Schools located west of 39 degrees 19'E and north of 6 degrees 10'S harboured nearly all of the infections; the highest prevalence (55%) was found at Kinyasini where many B. globosus habitats occur nearby. The general level of understanding of kichocho was low (24%) and individual self-diagnosis was poor (sensitivity, 8.5%; specificity, 85%). Grouped freshwater-contact patterns of schoolchildren differed significantly between schools and correlated well with prevalence of infections within schools. Across the island the area of active transmission of S. haematobium to humans appears confined within the distribution of B. globosus. There was no epidemiological evidence to suggest any involvement of B. nasutus in local transmission, confirming previous laboratory findings. In areas where B. globosus occurs, targeted snail control should be considered, to reduce schistosome transmission.

Adolescent↗

Cardiac involvement is a constant finding in acute Chagas' disease: a clinical, parasitological and histopathological study.

During the last 8 years 58 acute cases of Chagas' disease were studied. Patients from an endemic area of the state of Barinas, Venezuela, showed fever (98%) and circulating forms of T. cruzi (100%), and were treated with oral benznidazole. The recorded mortality was 8.6%. Acute myocarditis was constantly found either in myocardial biopsies or at necropsy, even in patients without any other sign of cardiac compromise (36%), which was detected by chest X-ray in 58%, by 2D echocardiography in 52%, by resting ECG in 41% and by clinical findings in 27.5% of the patients. Cardiomegaly was due to pericardial effusion rather than ventricular dilatation in most instances. Treatment eliminated parasitemia but negativized serology in only 20% of patients. It also appeared to have little influence on the ongoing myocarditic process, emphasizing the need for better therapeutic schedules, able to avoid or control the early appearance of immunologic mechanisms and microcirculatory damage involved in the future development of chronic chagasic myocarditis.

Acute Disease↗

Environmental parasitology: What can parasites tell us about human impacts on the environment?

There are a variety of ways that environmental changes affect parasites, suggesting that information on parasites can indicate anthropogenic impacts. Parasitism may increase if the impact reduces host resistance or increases the density of intermediate or definitive hosts. Parasitism may decrease if definitive or intermediate host density declines or parasites suffer higher mortality directly (eg. from toxic effects on parasites) or indirectly (infected hosts suffer differentially high mortality). Although these scenarios are opposing, they can provide a rich set of predictions once we understand the true associations between each parasite and impact. In this review, Kevin Lafferty discusses how parasite ecologists have used and can use parasites to assess environmental quality.

Journal Article↗