Prevalence of zoonotic trematode parasites in fish fry and juveniles in fish farms of the Mekong Delta, Vietnam

Thien, Cu Pham; Dalsgaard, Anders; Nhan, Nguyen Thanh; Olsen, Annette; Murrell, K. D.

doi:10.1016/j.aquaculture.2009.06.033

Cited by 39 publications

(41 citation statements)

References 9 publications

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“…Examples of management practices that can be implemented are, e.g. keeping fish fry in cement or composite tanks in filtered water longer than the usual 2 to 7 days (Thien et al 2009) or changing feed management from a system where fish are fed with manure (Dung et al 2010) to a system with commercial fish food, a system in which FZT prevalence has been reported to be lower than in a system where fish are fed manure (Thien et al 2007).…”

Section: Discussionmentioning

confidence: 99%

Higher attack rate of fish-borne trematodes (Heterophyidae) in common carp fingerlings (Cyprinus carpio) at lower fish weight

et al. 2012

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Fish-borne zoonotic trematodes (FZTs) can cause pathology in humans. Fish weight was reported as important risk factor for transmission from snail to fish. However, in fingerlings, the relation between fish weight and infection is unknown. Aim was quantifying the effect of fish weight on infection probability, attack rate, and metacercariae burden of FZTs in common carps (Cyprinus carpio) between 1 and 20 g. Fish were either used as controls (n = 66) or exposed to 250 parapleurolophocercous cercariae (n = 254). Fish weight was analysed as continuous explanatory variable or classified in four categories with average weights of 0.7 g (n = 116), 4.0 g (n = 58), 8.2 g (n = 57) and 14.2 g (n = 23). The inverse relation between percentage of fish with metacercariae and fish weight is reflected in lower percentages of infected fish at higher weights [%infected = 100/(1 + e([-2.02+0.15 fish weight (g)])); p < 0.01], i.e. 89 %, 85 %, 63 % and 61 %, respectively, in the four groups. Control fish did not get infected. Attack rates were 0.0087, 0.0073, 0.0040 and 0.0033 fish infected per cercariae, respectively; the first two attack rates being significantly higher than the latter two. Mean number of metacercariae per weight group was 5, 5, 2 and 1, respectively, (p < 0.05), with an inverse relation using weight as continuous explanatory variable [p < 0.01; number metacercariae = e(1.76-0.13fish weight(g))]. Concluding, an inverse relation exists between fish weight and probability of infection, attack rate and parasite burden in common carp fingerlings. Reducing transmission to fingerlings might be an effective intervention method to improve food safety, reduce the absolute amount of FZTs in the environment and eventually reduce incidence in humans.

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Section: Discussionmentioning

confidence: 99%

Higher attack rate of fish-borne trematodes (Heterophyidae) in common carp fingerlings (Cyprinus carpio) at lower fish weight

et al. 2012

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“…Evidence from Vietnam indicates that nursery stock was frequently infected with fish-borne zoonotic trematodes. 36 Our own preliminary data suggest that both hatchery and nursery stock in Lao PDR can be infected with O. viverrini, depending on the fish species (Sithithaworn P and others, unpublished data). (2) Snails with high prevalence were collected throughout the year, suggesting that climate is not a key factor.…”

Section: Resultsmentioning

confidence: 99%

Exceptionally High Prevalence of Infection of Bithynia siamensis goniomphalos with Opisthorchis viverrini Cercariae in Different Wetlands in Thailand and Lao PDR

Kiatsopit

Sithithaworn²,

Saijuntha³

et al. 2012

The American Society of Tropical Medicine and Hygiene

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Abstract. The carcinogenic liver fluke, Opisthorchis viverrini, requires Bithynia snail intermediate hosts in its life cycle. However, the prevalence of O. viverrini in snail intermediate hosts is typically low ( 1%). Here, we examined B. siamensis goniomphalos from 48 localities in Thailand and The Lao People's Democratic Republic (Lao PDR) and reported highprevalence levels of O. viverrini. The highest-prevalence levels per locality were 6.93% (mean = 3.04%) in Thailand and 8.37% (mean = 2.01%) in Lao PDR; 4 of 13 localities examined showed prevalence higher than any prevalence previously recorded. The number of cercariae infecting snails and their prevalence were positively correlated with the size of the snails. High prevalence occurred in the Songkram River wetland (Thailand) and the Nam Ngum River wetland (Lao PDR). Our results show that transmission of O. viverrini from humans as well as animal reservoir hosts to snail intermediate hosts is ongoing and potentially increasing in endemic areas across Thailand and Lao PDR.

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“…Fish for seeding are produced in hatcheries and after about one week, fry is transferred to nursing ponds, where they will be kept for about 9 weeks before being sold for grow-out farmers. Previous studies have shown that fry leaving the hatcheries are free from infection with FZT [27], while transmission is intense in nursing ponds [6,28] and grow-out ponds [6,10,28,29]. …”

Section: Introductionmentioning

confidence: 99%

Use of black carp (Mylopharyngodon piceus) in biological control of intermediate host snails of fish-borne zoonotic trematodes in nursery ponds in the Red River Delta, Vietnam

et al. 2013

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BackgroundThe risks of fish-borne zoonotic trematodes (FZT) to human health constitute an important problem in Vietnam. The infection of humans with these trematodes, such as small liver trematodes (Clonorchis sinensis and Opisthorchis viverrini), intestinal trematodes (Heterophyidae) and others is often thought to be linked to fish culture in areas where the habit of eating raw fish is common. Juvenile fish produced in nurseries are often heavily infected with FZT and since fishes are sold to aquaculture facilities for growth, control of FZT in these fishes should be given priority. Controlling the first intermediate host (i.e., freshwater gastropods), would be an attractive approach, if feasible. The black carp, Mylopharyngodon piceus, is a well-known predator of freshwater snails and is already used successfully for biological control of snails in various parts of the world including Vietnam. Here we report the first trials using it for biological control of intermediate host snails in nursery ponds stocked with 1-week old fry (10–12 mm in length) of Indian carp, Labeo rohita.MethodsSemi-field and field experiments were set up to test the effect of black carp on snail populations. In the semi-field experiment a known quantity of snails was initially introduced into a pond which was subsequently stocked with black carp. In the field trial in nursery ponds, density of snails was estimated prior to a nursing cycle and at the end of the cycle (after 9 weeks).ResultsThe results showed that black carp affect the density of snail populations in both semi-field and field conditions. The standing crop of snails in nursery ponds, however, was too high for 2 specimens to greatly reduce snail density within the relatively short nursing cycle.ConclusionsWe conclude that the black carp can be used in nursery ponds in Northern Vietnam for snail control. Juvenile black carp weighing 100 - 200g should be used because this size primarily prey on intermediate hosts of FZT and other studies have shown that it does not prey on fish fry of other species. It may be necessary to use a high stocking density of black carp or to reduce snail density in the nursery ponds using other measures (e.g. mud removal) prior to stocking fry in order for the black carp to keep the density of intermediate host snails at a very low level.

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Prevalence of zoonotic trematode parasites in fish fry and juveniles in fish farms of the Mekong Delta, Vietnam

Cited by 39 publications

References 9 publications

Higher attack rate of fish-borne trematodes (Heterophyidae) in common carp fingerlings (Cyprinus carpio) at lower fish weight

Higher attack rate of fish-borne trematodes (Heterophyidae) in common carp fingerlings (Cyprinus carpio) at lower fish weight

Exceptionally High Prevalence of Infection of Bithynia siamensis goniomphalos with Opisthorchis viverrini Cercariae in Different Wetlands in Thailand and Lao PDR

Use of black carp (Mylopharyngodon piceus) in biological control of intermediate host snails of fish-borne zoonotic trematodes in nursery ponds in the Red River Delta, Vietnam

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