Dynamics of <i>Centrocestus armatus</i> Transmission in Endemic River in Hyogo Prefecture, Japan

<i>Centrocestus armatus</i> is an intestinal parasite belonging to the family Heterophyidae. We developed an apparatus for recovering cercariae and clarified the infection dynamics of this parasite. To clarify the circadian rhythm of cercarial shedding in the summer season, we filtrated 30 l of river water every 2 h for 24 h. Cercariae were first detected between 06:00 and 08:00 h, increased over time to reach peak at 16:00 h and decreased thereafter, thus showing a single-peak pattern. In a survey of seasonal change, approximately 200 cercariae were contained in 1 l of river water during the summer season, while none were found during the winter. This cercarial shedding pattern appeared to be related to sunrise/sunset and water/atmosphere temperature. Therefore, we examined whether cercarial shedding was affected by light or temperature changes under laboratory conditions, and confirmed that both light and temperature were important factors for cercarial shedding. Light was a stronger factor than water temperature. Cercarial shedding of <i>C.</i> <i>armatus</i> occurred in response to temperature and light. The change in the number of juvenile metacercariae detected in fish brain corresponded with monthly detection rates of cercariae; however, the incidence of new infections decreased in August. This suggests that <i>Nipponocypris temminkii</i> contains a defense mechanism against new infections that may have hindered the increase in parasite infectivity. These results clarified the smooth infection from the first to the second intermediate host of <i>C. armatus</i> in the endemic river. Throughout the study period, fecal samples were collected from 19 kites, 114 herons, and three unidentified species. However, our results using <i>C. armatus</i> showed a low value of 1% in herons and 5% in kites. The infection dynamics of final host to first intermediate host need to be further investigated.

Review of Parasitic Zoonoses in Egypt

This review presents a comprehensive picture of the zoonotic parasitic diseases in Egypt, with particular reference to their relative prevalence among humans, animal reservoirs of infection, and sources of human infection. A review of the available literature indicates that many parasitic zoonoses are endemic in Egypt. Intestinal infections of parasitic zoonoses are widespread and are the leading cause of diarrhea, particularly among children and residents of rural areas. Some parasitic zoonoses are confined to specific geographic areas in Egypt, such as cutaneous leishmaniasis and zoonotic babesiosis in the Sinai. Other areas have a past history of a certain parasitic zoonoses, such as visceral leishmaniasis in the El-Agamy area in Alexandria. As a result of the implementation of control programs, a marked decrease in the prevalence of other zoonoses, such as schistosomiasis and fascioliasis has been observed. Animal reservoirs of parasitic zoonoses have been identified in Egypt, especially in rodents, stray dogs and cats, as well as vectors, typically mosquitoes and ticks, which constitute potential risks for disease transmission. Prevention and control programs against sources and reservoirs of zoonoses should be planned by public health and veterinary officers based on reliable information from systematic surveillance.

Experimental Toxocara cati Infection in Gerbils and Rats

Mongolian gerbils and Wistar rats were inoculated orally with 240 and 2,500 Toxocara cati embryonated eggs, respectively, to evaluate the larval recovery in different tissues and organs, such as the liver, lungs, heart, kidney, and skeletal muscles after 5, 30, 49, 70, and 92 days post-infection (PI). Larval recovery rates were 1.7-30.0% in Mongolian gerbils on days 5-92 PI and 0.2-3.8% in rats on the same days. These results indicate that Mongolian gerbils and Wistar rats are suitable experimental paratenic hosts for the study of neurological toxocariasis as well as visceral toxocariasis.

The correlation between contamination of soil with Ascaris sp. eggs in school yards and ascariasis among primary school children in Mai Trung Commune, Northern Vietnam

Four hundred and six soil samples collected from five schoolyards in Mai Trung Commune, Bac Giang Province, Northern Vietnam, from 2005 to 2007 were examined for helminth eggs using a sucrose centrifugal flotation method. The soils around latrines was found to be heavily contaminated with <I>Ascaris</I> sp. eggs. The contamination rate of Ascaris sp. eggs at each school and prevalence of ascariasis among the school children showed a positive correlation (P&It;0.05). This indicated that examination of soil from the area around latrines for <I>Ascaris</I> sp. eggs is a useful method to estimate the prevalence of ascariasis among school children.

Parasite egg contamination of water and air in a suburban area of Hanoi, Vietnam

Contamination of water and air by soil-transmitted helminth eggs was investigated in a small village located in the suburbs of Hanoi, Vietnam. Water samples were collected from 29 households, two schools, two kindergartens, one restaurant, three ponds and 23 ditch sites during the rainy season. Water samples were also collected at the same places, except for one household and one restaurant, during the dry season. The water samples collected from households, schools, kindergartens and restaurant were comprised of well-water and rain-water. These samples included both water filtrated with sand and gravel and non-filtrated water. Two-liter water samples were examined for helminth eggs by either a centrifugation or flotation method. The contamination of air by helminth eggs was assessed by the method of Kroeger <I>et al</I>. (1992). Eggs in air were trapped on adhesive tapes hanging in rooms and in the area around 29 houses, two schools, two kindergartens, one restaurant and 18 utility poles.<br>Out of 63 water samples collected from households in the rainy season, helminth eggs were found in four water samples; one from non-filtrated well-water and three from filtrated well-water samples. The one non-filtrated water sample contained six eggs of <I>Toxocara</I> sp., while the three filtrated water samples contained one egg each of <I>Trichuris</I> sp., <I>Trichiuris</I> sp. and <I>Taenia</I> sp. No eggs were found in the water samples collected from schools, kindergartens or the restaurant in the rainy season. All water samples collected from ponds and ditches in the rainy season contained many helminth eggs. The eggs found were <I>Ascaris</I> sp., <I>Trichuris</I> sp., <I>Toxocara</I> sp., <I>Ascaridia galli</I>, hookworm, <I>Taenia</I> sp. and <I>Fasciola</I> sp. Examination of the adhesive tapes hanging in the air showed that four sites were contaminated by helminth eggs, i. e. one site near the house, two sites near the school and one site at a utility pole. The species of eggs found were <I>Trichuris</I> sp., <I>Ascaridia galli</I> and <I>Taenia</I> sp. The number of eggs found on tapes was only one or two. In the dry season, a few samples of well-water and rain-water collected from the residential area were contaminated with helminth eggs, and all samples collected from ponds and ditches contained many eggs of various species similar to those collected in the rainy season. The present study clearly indicates that, in our study area, the villagers were subject to infection from soil-transmitted helminthes directly and indirectly through water.

CRYOPRESERVATION OF NEWBORN AND MUSCLE-STAGE LARVAE OF TRICHINELLA NATIVA

We examined the basic conditions for cryopreservation of newborn and muscle-stage larvae of Trichinella nativa. Two types of cryoprotectants were examined: dimethyl sulfoxide and glycerol. For cryopreservation of newborn larvae, dimethyl sulfoxide had a cryoprotective effect, and a maximum survival of 96% was obtained under conditions of 10% dimethyl sulfoxide and 30 min equilibration. Muscle-stage larvae, on the other hand, demonstrated a relatively high survival rate (approximately 80%) with 25% glycerol and three hours equilibration regardless of freezing rate. The infectivity of cryopreserved newborn and muscle-stage larvae was examined using different infection methods: direct injection into the abdominal cavity in the former, and either oral infection or direct injection into the duodenum in the later. Cryopreserved newborn larvae showed infectivity to all the subjected mice. By contrast, muscle-stage larvae did not show any infection when infected orally, but one mouse was positive when the larvae were injected directly into the duodenum.

Epidemiological study on Centrocestus armatus metacercariae in the Chikusa River, Hyogo Prefecture, Japan

The prevalence of <I>Centrocestus armatus</I> metacercariae in fresh water fishes were examined in Hyogo Prefecture, western Japan for a period of one year from April 2003 to March 2004. Three species of cyprinoid fish, namely <I>Zacco temminckii, Zacco platypus,</I> and <I>Pseudogobio esocinus,</I> were found to harbor metacercariae of <I>C. armatus.</I> The infection rate of metacercariae in <I>Zacco temminckii, Zacco platypus,</I> and <I>Pseudogobio esocinus</I> was 99% (371⁄377), 100% (8⁄8), and 100% (2⁄2), respectively. The mean number of metacercariae recovered was 232 for <I>Z. temminckii,</I> 2,123 for <I>Z. platypus,</I> and 20 for <I>P. esocinus.</I> However, we focused on <I>Z. temminckii</I> in this study because it was found to be the most predominant fish species in the Chikusa River and to have high a metacercariae prevalence as well. <I>In Z. temminckii,</I> metacercariae were distributed in the brain (37%), viscera (35%), muscles (29%) and gills (0%). No metacercariae were recovered from the scales and fins. This is the first report of the occurrence of <I>C. armatus</I> metacercariae in the brain region of the second intermediate fish. The prevalence of <I>C. armatus</I> metacercariae was almost constant throughout the year, and no positive correlation was found between the prevalence and seasonal changes. However, a positive relationship was observed between prevalence of metacercariae and fish length, I.e., the intensity of infection increases with the size of the fish host (p < 0.05). People in the survey area sometimes eat fish raw, indicating enlightenment as well as the countermeasures to prevent <I>C. armatus</I> infection is needed.

Detection of Giardia cysts in sewage and estimations of giardiasis prevalence among inhabitants in Hyogo Prefecture, Japan

We recovered <I>Giardia</I> cysts from sewage and estimated the prevalence of giardiasis among inhabitants in Hyogo Prefecture, western Japan. Two 200-ml sewage samples were collected once a month from two different sewage plants (A and B) during a one-year period. After pretreating the samples by filtration and centrifugation in the presence of alcohol and diethyl ether, an immunomagnetic separation method was applied to isolate <I>Giardia</I> cysts. The mean number of cysts recovered from plants A and B were 880⁄L and 2,000⁄L, respectively. Circadian rhythms in the number of cysts detected on each of two examination days were observed with a peak at 10:00 a.m., and seasonal variations in cyst numbers were also observed with two peaks in May and December. By using the data obtained from this survey, we estimated that the prevalence of <I>Giardia</I> infection in habitants in the areas serviced by plants A and B were 0.1-1.1 and 0.1-1.3%, respectively.