A. Tamburrini

Long-term survival of Cryptosporidium parvum oocysts in seawater and in experimentally infected mussels (Mytilus galloprovincialis).

Transmission of infectious oocysts of Cryptosporidium parvum via surface- and drinking-water supplies has been reported and many surface waters flow into the sea, potentially causing runoff of animal-infected faeces. Eating raw mussels is a common practice in many countries, increasing the publics risk of acquiring enteric pathogens. The aims of the present study were to estimate how long C. parvum oocysts remain infectious in artificial seawater, to determine if the oocysts are retained in mussel tissues (Mytilus galloprovincialis), and how long they maintain their infectivity. Oocysts were incubated in artificial seawater at 6-8 degrees C under moderate oxygenation and the infectivity of oocysts was tested five times, over a 12 month period after incubation in seawater, in BALB/c mice. Each pup was inoculated per os with 10(5) oocysts and killed 5 days p.i. Oocysts remained infectious for 1 year. Forty mussels held in an aquarium containing artificial seawater filtered out more than 4 x 10(8) oocysts in a 24 h period. Oocysts were detected in the gill washing up to 3 days p.i., in the haemolymph up to 7 days p.i., and in the intestinal tract up to 14 days p.i. Oocysts collected from the gut of mussels 7 and 14 days p.i. were observed to have infected mice. These results suggest that C. parvum oocysts can survive in seawater for at least 1 year and can be filtered out by benthic mussels, retaining their infectivity up to 14 days, so seawater and molluscs are a potential source of C. parvum infection for humans.

First Outbreak of Human Trichinellosis Caused by Trichinella pseudospiralis

This is the first report of an epidemic of human infection with Trichinella pseudospiralis. An outbreak of trichinellosis affecting 59 individuals, of whom one died, occurred in southern Thailand during 1994-1995. The source of this epidemic was raw pork from a wild pig that was distributed to villagers by a local hunter. The most striking clinical features among 50 individuals who could be followed were muscular swelling, myalgia, and asthenia persisting for > 4 months. These were associated with significant elevations of creatine phosphokinase and lactate dehydrogenase levels. All patients had Trichinella-specific IgG antibodies in an enzyme-linked immunosorbent assay. Muscle biopsies, performed in six cases, showed nonencapsulated, actively migrating Trichinella larvae. Experimental infection of mice with larvae from human biopsies revealed nonencapsulated muscle larvae consistent with T. pseudospiralis. The identification of muscle larvae from a human specimen by random amplified polymorphic DNA analysis confirmed the causative agent to be T. pseudospiralis. Patients seemed to respond best to treatment with albendazole.

Failure of Mebendazole in the Treatment of Humans with Trichinella spiralis Infection at the Stage of Encapsulating Larvae

Trichinella spiralis larvae infective for laboratory mice were collected from muscle biopsies performed at different times (from 1 day to 16 months) following the end of treatment, indicating the failure of mebendazole to kill Trichinella parasites when they are encapsulating in muscles.

Identification of a human isolate of Encephalitozoon cuniculi type I from Italy

A microsporidial strain, obtained from a person with AIDS living in Italy was isolated and cultivated on RK13 (rabbit kidney) cell monolayers. Identification at the species level was performed by immunological and molecular methods. Western blot analysis showed that the human isolate and the Encephalitozoon cuniculi reference strain had similar banding patterns. The small subunit rRNA sequence analysis confirmed the identification of the isolate as E. cuniculi, which is a widespread microsporidian species infecting a wide range of natural hosts, including humans. Moreover, based on the sequence of the rDNA internal transcribed spacer region, this isolate was classified as E. cuniculi type I (rabbit strain), previously reported in six persons with AIDS living in Switzerland. These results provide further information on the geographical distribution of E. cuniculi types.

Detection of Trichinella spiralis in a horse during routine examination in Italy

Routine examination for Trichinella infection by artificial digestion of 5-g samples of muscle tissue revealed the presence of muscle larvae in one out of 28 horses imported from Romania to an abattoir in Italy. The parasite, identified as Trichinella spiralis by the polymerase chain reaction, showed a reproductive capacity index of 68 in Swiss mice. Light microscope examination of 200 nurse cell-larva complexes showed that 22% of them were calcified and that the capsules of the non-calcified nurse cells were 17.5-27.5 microns (s = 22.67 microns) thick and had very few cellular infiltrates. The serum samples from the parasitologically positive horse and from three other horses of the same stock, from which Trichinella larvae were not recovered by digestion, showed a low level of positivity as determined by ELISA and Western blot analyses using a crude antigen, whereas negative results were observed in both tests when an excretory-secretory antigen was used. The results, together with data from the literature, suggest that the horse had acquired the infection 8-10 months previously and confirm earlier observation obtained from experimental infections, which showed that muscle worm burden and specific circulating antibodies were lost several months after infection.

Distribution of Trichinella spiralis larvae in muscles from a naturally infected horse

Epidemiological investigations conducted during 10 trichinellosis outbreaks between 1975 and 1994 showed that horse-meat was the probable source of infection. Though hundreds of thousands of horses have been examined at abattoirs in America and Europe to detect Trichinella infection by artificial digestion or trichinelloscopy, an infected horse has never been detected during routine analysis, which consists of examining 1 g of tissue muscle from the diaphragm. In November 1996, a naturally infected horse imported from Romania was detected in Southern Italy. The parasite was identified as Trichinella spiralis by random amplified polymorphic DNA analysis. Artificial digestion of tissue samples from 60 different muscles from 13 different sites of the infected horse carcass showed that M. levator Labii maxillaris, M. hyoideus transversus, and M. buccinator were the 3 most infected muscles. Muscles from the tongue, the masseter, and the diaphragm, which have normally been considered the muscles of choice for diagnosis, were the 4th, 6th and 13th most infected muscles, respectively. When comparing body sites, muscle tissues from the head showed the highest level of infection, followed by muscles from the neck. This finding may explain the negative results that have been obtained in the past during routine examination of the diaphragm of horses.