ِAnimal Health Research Institute,

Assiut Regional Laboratory.

Studies on some clinostomatid metacercariae from Tilapia nilotica

in Assiut Governorate

(With 4 Tables and 6 Figures)

By

M.I. Arafa; Maha S. Shaheen*

and M. EL Salahy M.Monib*

               *Dept. of Parasitology Fac. of Medicine, Assiut Univ.                      

)Received at 29/9/2005)

دراسات علي بعض ميتاسرکاريا الکلينوستوماتيد من أسماک البلطي

بمحافظة أسيوط

محسن ابراهيم عرفة ، مها سيد شاهين ، محمد الصلاحى محمد منيب.

أجريت هذه الدراسة على عدد 175 من أسماک البلطى النيلى فى محافظة أسيوط لعمل بعض الدراسات على ميتاسرکارياالکلينوستوماتيد التى تصيب تلک الاسماک. بلغت نسبة الاصابة بالانواع المختلفة من الميتاسرکاريا 42.86 % وکان التجويف الخيشومى هو أکثر الأماکن تعرضا للأصابة حيث بلغت نسبة الاصابة بة 29.27 % أما فى الکلى فکانت نسبة الأصابة 13.71% بينما بلغت نسبة الأصابة فى عضلات الفک السفلى 2.29%. وقد وجدت 1.71 % من الميتاسرکاريا غير متحوصلة وکانت تتحرک بين العضلات وفى التجويف الخيشومى. وتم تصنيف اربعة أنواع من الميتاسرکاريا فى أسماک البلطى وهى: کلينوستومم فالاکروکوراسز،کلينوستومم کومبلاناتم, کلينوستومم تيلابيا, إيوکلينوستومم ارديولا. وکذلک تم الوصف المورفولوجى لکل نوع من أنواع الميتاسرکاريا السابقة. کما تم وصف نويع جديد من ميتاسرکاريا الکلينوستومم فالاکروکوراسزلأول مرة فى أسماک البلطى فى أسيوط وکذلکالتغيرات المورفولوجيةغير الطبيعية التى وجدت فى احدى ميتاسرکاريا الأيوکلينوستوم ارديولا.

Summary

A total number of 175 fishes (Tilapia nilotica) were investigated for parasitological studies on some Clinostomum metacercariae in Assiut city. The results revealed that 42.86% of examined fishes were infected with different species of metacercariae. The gill chamber was the most common habitat of infection where their infection rate was 29.27% followed by kidneys 13.71% then mandible muscles 2.29%. In 1.71% of infected fishes the metcercariae were detected actively motile in both gill chamber and between muscle bundles. Four species of metacercariae were detected in the present work: Clinostomum phalacrocoracis, Cl. tilapiae, Cl. complanatum and Euclinstomum ardeola. The morphological characters of each species of the detected metacercariae were described. More over a new variety of Cl. phalacrocoracis was described for the first time in Tilapia nilotica in Assiut. Abnormal morphological changes also were described in one metacercaria of Euclinstomum ardeola.

Key words:Clinostomatid, metacercariae, Tilapia nilotica.

Introduction

Fishes could be considered as one of the main source of animal protein and in some countries they constitute the main food stuff beside the other nutritional substances.

Parasitic diseases in warm water fishes are considered serious problems are rather than bacterial diseases (Axelord & Snieszko 1980). They may lead to economical losses in body weight as well as a public health significance in certain circumstances (Stoskopf, 1993). The metacercariae of  family Clinostomatidae are known to encyst in fish  and frogs while their adults are parasites of  fresh water  fish and frog eating  reptiles, birds and mammals (Malek, 1980; Beaver et al., 1984) these metacercariae known as the yellow grub and cause considerable damage to the tissues of the fish host (Katantan et al., 1987). Clinostomum metacercariae, like Fasciola and Pentastomes have been known to cause a clinical syndrome called halzoun or marrara in humans as a result of eating raw or insufficient cooked fresh-water fish (Chung et al., 1995). Human laryngitis as a result of infection with metacercariae of Clinostomum complanatum was recorded in many countries as Japan ,India and Israel (Witenberg 1944, Cameron 1945, and Isobe et al., 1994).

The aim of the present work was to estimate the prevalence ofclinostomatid metacercariae parasitized Tilapia nilotica in Assiut Governorate in addition to identify of the detected metacercariae.  

Materials and Methods

One hundred and seventy five fresh water fishes (Tilapia nilotica) were collected from fish markets of Assiut city. Fishes were carefully opened and examined immediately (gills, branchial, pharyngeal regions and kidney) by naked eye for the presence of metacrecarial cysts.

- Encysted metacercariae were collected, excysted and compressed between two glass slides and examined under microscope (Eissa & Halla, 1993). They were fixed, stained with acetic alum carmine and mounted in canada balsam (Kurse & Pritchard, 1982).

- Identification was done according to the keys given by Yamaguti (1958) and Ukoli (1966).

- The detected metacercariae were measured and photomicrographed by using dissecting microscope.

Results

Out of 175 Tilapia nilotica examined in Assiut city, 75(42.86%) were infected with different species of clinostomatid metacercariae (Table 1). Metacercariae were detected in both gill chamber, kidneys and mandible muscles, the ratio of infection of each one was 29.71%, 13.71% and 2.29 % respectively. Most metacercariae detected in the present work were seen as a small cyst, but in three cases (1.71%) actively motile metacercariae were found actively moving between gill fibers and muscle bundles. Mixed infection by more than one species of metacercariae was detected in 5(2.86%) of examined fishes. Morphologically four species of metacercariae were identified in the present work (Table 2):

  -Clinostomum phalacrocoracis& new variety of Cl. phalacrocorasis.

  - Cl. complanatum.                          

  -  Cl. tilapiae.                                 

-Euclinstomum ardeola  (normal and abnormal).

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The morphological characters and measurementsof each one are presented at Tables 3-4 and Fig 1-6.

Table 1: Prevalence of different metacercariae were detected in examined fish.

Table 2: Prevalence of different species of clinostomatid metacercariae

were detected in the present work.

* Mixed infection was detected in five cases.

Table 3: Measurements & characters of different Clinostomum metacercariae were detected in the present work. (All measurements are in millimeters)             

Table 4: Measurements & characters of Euclinostomum ardeola metacercariae (normal & abnormal) detected in the present work. (All measurements are in millimeters)

    1- Clinostomum phalacrocoracis ×3.3.

    2- A new variety of Clinostomum phalacrocoracis× 3.6.

    3- Cl. complanatum ×8.2.

    4- Cl. tilapiae ×8.2.                                

    5- Euclinstomum ardeola (Normal shape) × 4.4.

    6- Euclinstomum ardeola (Abnormalshape) ×4.4.

Discussion

          This study confirmed that different species of clinostomatid metacercariae have been indigenously distributed in Tilapia nilotica in Egypt. Among one hundred and seventy five fish examined in the present work (42.86%) were infected with different species of metacercariae .This result is considered lower than that recorded by: Awad (1992) from River Nile (68.65%) and Khattab (1992) in Giza (87.06%) but is higher than that recorded by Shaheen (1998) in the same locality (29.2%).

   Such difference might be attributed to the food supply, the water resources (Nile or canals), and availability of snail intermediate host which play the main role for complete the life cycle of these parasites. Regarding the habitat of metacercariae in examined fishes, it the first time to detect of Clinostomum metacercariae in muscle bundles of mandible, but the gill chamber is the most common habitat  for them (29.71%). This result might be attributed to that the gill chamber is considered a highly bloody region in the fish body. The same result was recorded by Eissa et al. (1996) and Shaheen (1998). Concerning the actively motile metacercariae which were detected in (1.71%) of examined fishes this result may be due to exposure of fishes during marketing to high temperature specially in summer season. Asanji &Williams (1975) mentioned that the optimum temperature of excyctement of Clinostomum metacercariae is 37- 42˚C.

Morphologically, metacercariae of the present work were differentiated into two genera: Clinostomum and Euclinostomum. According to key provided by Ukoli (1966) Clinostomum metacercaria of the present work were identified as three species: Clinostomum phalacrocoracis, Cl. complanatum and Cl. tilapiae. Cl. phalacrocoracis metacercaria showed the highest infection rate (28.6%) followed by Cl. complanatum (2.29%) and Cl. tilapiae (1.14%). This result agree with that recorded by Eissa et al. (1996) and lower than that mentioned by Eissa and Hala (1993)

A close study of the morphological characters and measurements of Cl. phalacrocoracis metacercariae revealed that one specimen has several morphological variations as the following:

-          Their body distinctly divided into two parts where their fore-body is conical shape while the hind-body is elongate lanceolated shape.

-          The anterior end is blunt while the posterior end slightly pointed.

-          Both testes are triangular (not fan shape) and asymmetrical.

-          The ventral sucker is rounded in outline.

-          The distance between anterior and ventral sucker is greater.

-          Both ovary and cirrus pouch are located at the left side.

-          Longer distance between the ventral sucker and anterior testis.

As shown above, the present specimen definitely differentiated from Cl. Phalacrocoracis metacercariae for which we considered it as a new variety of Cl. Phalacrocoracis waiting for further investigation to confirm the identification and to elucidate their life cycle.

Concerning to the metacercariae of Euclinostomum sp. in the present work it was identified as Euclinostomum ardeola according to the description of Donges (1974), El-Naffar & Khalifa (1981) and Zedan (1983).

Among Euclinostomum metacercariae which were examined in the present work abnormal morphological characterswere detected in one specimen as the following:

  1- Absence of posterior testis.

  2- Abnormal shape of anterior testis.

  3-Unequal numbers of intestinal diverticula.

  4- The uterine sac is shorter.

These abnormalities may be related to several factors ether internal (way of insemination & senility) or external (environmental factors). Nollen (1988) mentioned that some species of platyhelminths undergo abnormal growth specially their sexual development in case of self- insemination. Thorogood (1997) mentioned that the actual incidence of trematod anomalies may vary according to: host, environmental/teratogenic factors including drugs, polygenic disorders, single gene mutations and others. 

Conclusion

 The infection of Tilapia nilotica with Clinostomum metacercariae should be seriously considered because it can cause an economic loss and a public health problem. Among these species Cl. complanatum metacercariae is necessary to pay more attention, where it causes severe damage of infected fish in addition to human laryngo- pharyngitis as a result of eating of fresh water fish or incomplete cooked fish (Williams and Jones 1976). Previous authors detected few enzootic foci of Cl. complanatum in the world. This study is confirm the presence of Cl. complanatum in Assiut Governorate, where it was detected previously by Shaheen (1998). Further studies should be done on other species of fishes and wild birds suspected as natural final host of most Clinostomum metacercariae for identification of their life cycle.

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