Application of the Midi Parasep® SF technique for the detection of L1 larvae of Angiostrongylus cantonensis in faeces of infected rats.

We investigated parasitic zoonoses caused by protozoans and helminths in urban and peri-urban rat populations (Rattus norvegicus and R. rattus) in Spanish cities. Rats were trapped and then dissected to remove adult helminths, and the contents of the large intestine were retrieved for the study of parasitic forms. The Midi Parasep® solvent free (SF) technique was used to concentrate the parasites in the intestinal contents. Some of the rats studied (n = 8) were infected by the rat lungworm, Angiostongylus cantonensis, whose first stage larvae (L1) are shed in rat faeces. After the concentration technique, L1 larvae were found in the sediment of 6 of the 8 positive rats. The two negative sediment samples were due to the presence of either only adult females or, in addition to males, only young females in the lungs of the rats. In view of our results, Midi Parasep® SF turned out to be a simple, rapid, inexpensive, and sensitive method to detect nematode larvae, such as the L1 larvae of A. cantonensis (or A. costaricensis), in natural and experimentally infected rats.

The helminth community component species of the wood mouse as biological tags of a ten post-fire-year regeneration process in a Mediterranean ecosystem.

Serra Calderona Natural Park, a Mediterranean ecosystem, has been in post-fire regeneration for 10 years. To elucidate which helminth community component species of the wood mouse, Apodemus sylvaticus, can be considered biological tags of this process, the influence of intrinsic (host density; host sex and age) and extrinsic factors (site, year, and period of capture; vegetation recovery) on their prevalence and abundance has been analysed, comparing a burned and an unburned area. A total of 564 wood mice (408 from the burned and 156 from the unburned area), from the 2nd to the10th post-fire year, was included in this helminthoecological study. The results suggest that the area in post-fire regeneration is still more vulnerable to periodic environmental changes than the unburned area as deduced from the analysis of the helminth populations of Pseudocatenotaenia matovi, Skrjabinotaenia lobata, Trichuris muris, Eucoleus bacillatus and Aonchotheca annulosa. The intermediate and definitive host populations presented a greater variability to these environmental changes in the burned area (Taenia parva, P. matovi, S. lobata, A. annulosa, Syphacia stroma and S. frederici). In the regenerating area, some behavioural changes in certain populations determined by the host sex are taking place (T. parva, Helgimosomoides polygyrus and S. frederici). During the last years studied, a greater similarity in the populational development of some component species between both areas can be appreciated (H. polygyrus and S. stroma). The role of the wood mouse and its helminth parasites as biological tags of the post-fire regeneration process in Mediterranean ecosystems has been confirmed.

Updating Taenia asiatica in humans and pigs.

An epidemiological study on taeniasis and cysticercosis in northern India has recently updated the epidemiology of Taenia asiatica. Practically, all the detected cases of taeniasis were caused by T. asiatica, cited for the first time in humans in that country. The finding widens the geographical distribution of T. asiatica, a species wrongly considered an exclusive South-Eastern Asian parasite. Due to the introduction of molecular techniques in Taenia diagnosis, the species is slowly showing its true distribution. A human Taenia species with cosmopolitan hosts (the same as the other two Taenia species) but limited to a specific geographical area and not affected by globalisation would certainly be hard to believe. Regarding cysticercosis, there is a remarkable finding concerning T. asiatica pig cysticercosis, specifically the presence of the cysticercus of T. asiatica not only in the liver (its preferential infection site) but also in muscle. This is the first time that the cysticercus of T. asiatica has been found in muscle in a naturally infected pig. This fact is actually relevant since people are at a greater risk of becoming infected by T. asiatica than previously expected since the liver is no longer the only site of pig infection. The Taenia species causing Taenia saginata-like taeniasis around the world, as well as pig and human cysticercosis, should always be molecularly confirmed since T. asiatica could be involved.

First ultrastructural data on the human tapeworm Taenia asiatica eggs by scanning and transmission electron microscopy (SEM, TEM).

Humans are definitive hosts of three species of the Taenia genus, namely Taenia solium, Taenia saginata and Taenia asiatica. The relative novelty of the latter explains the lack of knowledge concerning certain relevant aspects related to this parasite, such as its definite geographical distribution and whether its eggs can infect humans or not. So far, only the eggs of T. solium are known to be infective for humans, producing cysticercosis. Although eggs contain the infective stage, the oncosphere, there is a lack of research on the ultrastructure of eggs of human taeniids. We show, for the first time, the ultrastructure of eggs of T. asiatica by means of SEM and TEM analyses. We detected all the envelopes, namely the egg shell, vitelline layer, outer embryophoric membrane, embryophore, granular layer, basal membrane, oncospheral membrane and oncospheral tegument. Hooks surrounded by myofibrils and glycogen-like particles, the two types of secretory granules of the penetration glands, as well as several nuclei and mitochondria were also revealed in the oncospheres. In addition to the already known structures in eggs from other Taenia species, the presence of two types of small vesicles is described herein, possibly corresponding to exosomes and ectosomes because of their shape and size, which could participate in the host/parasite intercellular communication.

Socio-environmental variables and transmission risk of lymphatic filariasis in central and northern Mozambique.

Lymphatic filariasis (LF) is endemic in Mozambique, where it is caused by Wuchereria bancrofti with Culex quinquefasciatus as the main vector. It affects approximately 10% of the population (2 million) with about 16 million at risk. Prevalence rates in 40 out of 65 districts that together comprise the four endemic provinces Niassa, Cabo Delgado, Nampula and Zambezia were analysed with the aim of elucidating the socio-environmental variables influencing the transmission. The levels of prevalence were divided into six ranks and certain climatic, environmental and social factors were considered independent variables. A climadiagram was created and the LF risk and the water budget-based index were calculated for each district. Factors influencing the risk of the overall transmission and that of the provincial levels were established by discriminant analysis. The results show that LF transmission increased with mean maximum temperature and decreased with altitude. The almost constant annual temperature (especially in the tropical area), altitude, general economic conditions and predominant crop production (rice) were found to be responsible for the abundance and presence of the vector. However, despite the presence of the vector in the hinterland, presence and survival of the parasite were not found to be favoured there. The transmission risk was found to be highest in Zambezia, and consequently also the prevalence, while the situation in Niassa was the opposite. The conclusion is that temperature, altitude and the development/poverty index (particularly in the urban areas) have to be considered as transmission risk factors for LF in Mozambique. The extent of rice culturing probably also plays a role with respect to this infection.

Taenia asiatica: the most neglected human Taenia and the possibility of cysticercosis.

Not only Taenia solium and Taenia saginata, but also Taenia asiatica infects humans. The last species is not included in the evaluation of the specificity of the immunodiagnostic techniques for taeniasis/cysticercosis. There is currently no specific immunodiagnostic method for T. asiatica available. Therefore, due to the fact that molecular techniques (the only tool to distinguish the 3 Taenia species) are normally not employed in routine diagnostic methods, the 2 questions concerning T. asiatica (its definite geographic distribution and its ability to cause human cysticercosis), remain open, turning T. asiatica into the most neglected agent of human taeniasis-cysticercosis.

Risk analysis of human anisakidosis through the consumption of the blue whiting, Micromesistius poutassou, sold at Spanish supermarkets.

European legislation directed at the catering industry concerning the prevention of anisakidosis proposes efficient measures to avoid human infestation, but this legislation does not directly address the consumer at the household level. Assessing the anisakidosis risk for consumers who buy fresh fish at supermarkets in Spain, 284 blue whiting, Micromesistius poutassou, specimens, originating from two fishing zones and seasons of capture, sold at five nationwide Spanish supermarket chains, were examined to identify the presence of anisakid species and analyze their prevalence and abundance in viscera and flesh. The potential influence of intrinsic (length and weight) and extrinsic (origin, season, and days after catch) factors was statistically analyzed. The only two species detected were Anisakis simplex complex and Hysterothylacium sp. Total anisakid prevalence was 55.6%, with A. simplex being more prevalent (53.9%) and abundant (3.9 helminths/fish), and also carrying the biggest risk for consumers. Origin (Atlantic and Mediterranean) and season (spring and autumn) were the most influential factors among those considered. Results suggest that specimens originating from the Atlantic, of greater weight and length, and caught in spring pose the highest transmission risk of anisakidosis. Moreover, the days passed between the catch and consumption should be considered as a risk factor. Thus, in addition to the recommendation of freezing fish at -20°C for at least 24 h (in case the fish is consumed raw or poorly cooked), new and easy-to-follow recommendations are being proposed to avoid anisakidosis at home, which emphasize the importance of the information provided on fish crate labels.