Proc.Zool.Soc.India. 16 (1) : 55 - 61 : (2017)ISSN 0972 - 6683 : INDEXED AND ABSTRACTED 11

Received - 21.01.2017 Accepted - 30.03.2017

ABSTRACT

Rattus rattus (n=65) were autopsied and their intestine examined for the presence of parasites. The intestine of 4 rats revealed whitish cestodes frequently attached to the intestinal wall and were identified as Hymenolepis nana (the dwarf tapeworm (length 22 to 43 mm; width 0.95-1.48 mm). Scolex anterior, small, globular, (diameter 0.31 mm), cup-like, tetrad (four suckers) and retractile rostellum (row of 20–30 hooks). Proglottid contains a single set of reproductive organs, genital pores unilateral. Testes three, ovary sub median, lobed (0.19-0.42 mm by 0.21-0.39 mm). Gravid proglottids (length 0.22–0.34 mm, width 0.81–0.94 mm) filled with numerous eggs. Vitellaria compact and small. Eggs slightly oval (average 53.71 X 42.29 micrometers).

Key words : Wild rat, cestode, Hymenolepis, dwarf tapeworm, rodent

INTRODUCTION

Hymenolepis nana (Cestoda: Taeniidae) is commonly known as the dwarf tapeworm and in the human body, it is the most frequently found cestode parasite. Infections are more common among children. It is most widespread in warm climates and around unsanitary areas where eggs can be passed through aecal matter from an infected host to an uninfected person. Hymenolepis nana can be found wherever humans and rodents live. They have been found in almost all types of terrestrial biomes. (Roberts and Janovy Jr., 2000). It lodges itself in the intestines and absorbs nutrients from the intestinal lumen (Cameron, 1956). Gupta et al. (1981) reported the effect of mode of infection on the development and chemotherapeutic response of H. nana in rats. In another report, the parasite occurred at an incidence of 9.9% in urban slum dwellers of India being highest amongst intestinal infections (Mirdha and Samantray, 2002).

Goswami et al. (2011) recorded Hymenolepis diminuta from albino wistar rats and wild brown rats. Gupta et al. (2013) observed the serum chemistry in pregnant and non-pregnant rats, infected with cestode parasite and the condition factor and organosomatic (hepato and splenosomatic) indices of Rattus rattus parasitized by cestodes were also reported (Gupta et al., 2016). Kumar et al. (2016) recorded changes in haemoglobin in wild rats, infected with Hymenolepis diminuta. The present investigations were undertaken to characterize the morphological features and taxometry of the cestode parasite based on the morphology of the scolex, segments and egg structures.

MATERIALS AND METHODS

COLLECTION AND MAINTENANCE OF HOSTS

R. rattus (150 – 320 g) were trapped alive in rat traps from storehouses and godowns of different areas of Bareilly, U.P. India and nearby places. Trapped rats were immediately transported to the laboratory, maintained in rat cages and fed on food grains, bread crumbs and water ad libitum. To avoid the effect of stress, rats were dissected and examined preferably within 24 hours from capture. They were anaesthetized humanely using chloroform anesthesia and weight, length and sexes were recorded before dissecting the animal.

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HYMENOLEPIS NANA FROM RATTUS RATTUS OF ROHILKHANDWITH A NOTE ON THEIR HAZARDS TO HUMANS

1 1D.K. GUPTA , NEELIMA GUPTA*2, SUDHIR KUMAR1Department of Zoology, Bareilly College, Bareilly 243005. India

2Centre of Excellence Laboratory, Department of Animal Science, MJP Rohilkhand University, Bareilly 243006. India

FAECAL EXAMINATION

The faecal samples were routinely examined macroscopically for the presence of cestode segments and microscopically by direct smear method for the presence of eggs.

ISOLATION AND PROCESSING OF CESTODES

Cestodes were found attached to the wall of the lumen with their suckers; therefore they were detached carefully with the help of a soft brush so that the scolex was not damaged. They were relaxed in normal saline. Often worms released eggs which was advantageous for cestode study as an egg lled uterus can hide the important reproductive structures which are essential for identication. The cestodes were washed with distilled water several times and xed in 10% formalin or Carnoy's uid.

Correctly xed and attened worms were stored in 70% alcohol in labeled glass vials. The parasites were stained with routine techniques (Gupta et al., 2016) in Borax carmine and eosin, dehydrated, cleared and mounted in canada balsam. Photographs were taken under Olympus BX-53 microscope and the parasites measured with Cellsens software imaging system.

RESULTS

Hymenolepis nana (synonyms Dwarf tapeworm, Rodentolepis (Hymenolepis) microstoma, Rodentolepsiasis, Vampirolepis nana, Hymenolepis diminuta, Mathevotaenia, Rat tapeworm)

TAXOMETRY

Phylum - Platyhelminthes

Class – Cestoda

Subclass – Eucestoda

Order - Cyclophyllidea

Family - Hymenolepididae

Genus – Hymenolepis, Rodentolepis

Species: nana

PARASITE PROFILE

Host Rattus rattus

Locality Bareilly (U.P.)

Prevalence 4/65

Mean intensity 1-3 parasites/host

POST MORTEM EXAMINATION

The faecal samples examined revealed the presence of cestode eggs bearing hooks. Such rats were further autopsied to investigate the presence of adult cestodes.

The intestine of 4 out of 65 autopsied rats revealed whitish cestodes frequently attached to the intestinal wall.

DESCRIPTION

ADULT (Fig. 1)

The worms were delicate, whitish and opaque when alive and the body is composed of proglottids (Fig. 1A). The adults of the dwarf tapeworm are 22 to 43 mm in length and 0.95-1.48 mm in width. Scolex is small, 0.31 mm in diameter, almost globular (rounded), cup-like, situated at the anterior end of body, tetrad having four suckers and retractile rostellum with a row of 20–30 hooks Fig. 1B,C).

Scolex was followed by a narrow slender neck with segments wider than long (Fig. 1D). The genital pores are unilateral, situated on the side of the segment. Each segment contains a single proglottid, with a single set of reproductive organs. Each proglottid has both male and female reproductive organs, thus Hymenolepis nana is hermaphroditic (Fig. 1E). Each mature segment contains three testes, oval to elongated in shape. In the posterior mature proglottids, cirrus was also observed. Ovary sub median,

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towards the aporal side, and lobed measuring 0.19-0.42 mm by 0.21-0.39 mm. Vagina thin walled and tubular, occasionally hardly visible. Gravid (mature, full of eggs) proglottids are 0.22–0.34 mm long and 0.81–0.94 mm wide. The gravid proglottid is lled with numerous eggs, and the uterus is not visible (Fig. 1F). Vitellaria compact and small. Proglottids were never present in the faeces and therefore presumably disintegrate in the gastrointestinal tract.

EGGS (Fig. 2) (measurements in µm)

The eggs of H. nana are slightly oval at about 47.22-56.63 (average 53.71) X 37.67-46.97 (average 42.29) micrometers (Fig. 2A). The eggs of H. nana did not have a striated appearance which is unlike other taeniid eggs ( Lapage, 1951; Roberts and Janovy Jr., 2000; Ghaffar, 2001). Eggs were freely observed in the infected faecal samples, they are embryonated when laid containing a well developed 6-hooked onchosphere [30.13 x 26.33] which was 11.99 (longitudinal axis) x 8.11 (transverse axis) away from the membrane (Fig. 2B,C). The hooks ranged from 8.50-15.2 in length. The oncosphere is covered with a thin, hyaline, outer membrane and an inner, thick membrane with polar thickenings, "knobs" or poles that bear four laments and spread out between the two membranes lying between the inner and outer membranes and this was similar to those reported by Ghaffar (2001). A few eggs were observed in the rupturing stage releasing the oncosphere (Fig. 2D). The heavy embryophores that give taeniid eggs their characteristic striated appearance are lacking in this and the other families of tapeworms infecting humans. The rostellum remains invaginated in the apex of the organ. Rostellar hooklets are shaped like tuning forks.

REMARKS

Many species of the genus Hymenolepis, Weinland, 1858 are known from rodents of different countries (Southwell,1930; Hughes, 1940; Lapage,1956; Yamaguti, 1959; Smyth,1962)

The present specimens were identied as Hymenolepis nana because they possessed characters similar to this parasite, such as rostellum with a row of 20 hooks, neck small, mature and gravid, segments similar to H. nana.

DIAGNOSIS

Diagnosis was based on nding eggs in the faecal samples.

LIFE CYCLE

The life cycle of the parasite was investigated earlier by Shorb (1933), Hunninen (1935), Kumazawa and Suzuki (1983) and Henderson and Hanna (1987), the latter authors provided valuable protocols for the maintenance of life cycle.

Adult development from cysticercoids

Rats 5-6 weeks old are suitable hosts. The cestodes establish themselves initially in the anterior small intestine but subsequently migrate to the lower ileum, where they remain for the duration of infection (Henderson and Hanna, 1987).

Adult development from eggs

In a direct egg infection, eggs hatch in the duodenum and oncospheres immediately penetrate the villi in which they develop into fully formed cysticercoids within 93-96 hours. The highest concentration of cysticercoides occurs in the region 100-200 mm from the pyloric sphincter. At about 102 hours, cysticercoids break out of the villi, envaginate and become attached in the posterior third of the gut. The pre-patent period varies somewhat between hosts, being 11-16 days in the rat (Shorb, 1933) and 14-25 days in mice (Hunninen, 1935). In rats, maximum eggs production occurs between 14 and 16 days. The life span is short, 12-24 days in rats and 2-56 days in mice.

Species Used as Host

Fleas, Siphonaptera

Flour beetles, Tenebrionidae

Caprophagus insects, Insecta

Rodents, Rodentia

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Humans, Homo sapiens

DISCUSSION

H. nana was rst identied as a human parasite by Von Siebold in 1852. In 1906, Stiles (cf Scott and Camb, 1923) identied an identical parasite with a rodent host and named it Hymenolepis fraterna. Later, morphological characteristics were used for taxonomy identication and H. nana was known to have hooks and linear reproductive organs. H. diminuta has no hooks and reproductive organs arranged in a triangular formation.

Some workers are of the opinion that this species should be renamed Vampirolepis nana but this designation is not widespread use. Often referred to as 'dwarf' tapeworm, this is a common parasite of rodents and also, of man, in whom it causes hymenolepiasis. Morphologically, it differs from H. diminuta chiey by the presence of well developed rostellum armed with a crown of hooks.

H. fusa was reported from India in birds by Southwell (1930). Bilqees and Siddiqui (1981) reported a similar cestode from rats in Karachi and identied it as H. fusa based on characters similar to H. fusa. H. nana infects the small intestine of rats. The present ndings are in accordance to earlier reports from India and abroad. The prevalence of the worm was 22% in UK (Webster and Macdonald, 1995), 31.3% in Iran (Sadjjadi and Massoud, 1999) whereas in the present case, the prevalence was quite low (6.15%). This tapeworm is signicant in the sense that it is capable of causing infection in humans too and thus has a zoonotic importance.

HAZARDS TO HUMANS

Hymenolepis nana is regarded as the most common cestode parasite found in humans (Roberts and Janovy, 2000). It can frequently be found in the intestines of humans and absorb nutrients from the intestinal lumen (Cameron, 1956). In adults, the parasite is mainly a nuisance instead of a health problem, but in children, its pathological manifestations may become dangerous. Usually it is the larva of this tapeworm that causes the most problem in children (Lapage, 1951). The larva burrows into the walls of the intestine, if there are enough tapeworms in the child, severe damage can be inicted. This is done by absorbing all the nutrition from the food the child eats (Lapage, 1951). Hymenolepis nana usually does not cause deaths unless in severe infectivity and usually young children or in people who have weakened immune systems, the pathogenecity may be high. In some parts of the world, heavily infected individuals are a result of internal autoinfection (Lapage, 1951; Cameron, 1956; Olsen, 1974; Roberts and Janovy Jr., 2000).

Patients with more than 15,000 eggs per gram of stool may experience cramps, diarrhoea, irritability, anorexia, or enteritis caused by cystercoids destroying the intestinal villi in which they develop. Symptoms include anal itching, diarrhcea (can be bloody), headache, increased appetite or loss of appetite, insomnia, muscle spasms, nausea, nervousness, seizures, stomach ache, vomiting, weakness, weight loss. In human adults, the tapeworm is more of a nuisance than a health problem, but in small children, many H. nana can be dangerous.

It can be concluded that in order to improve the wealth of information on the range and variation in the component community structures of the intestinal parasites in wild Indian rats from different regions of the world and from different climatic zones, the study should be taken up by more research groups across the country. The important position occupied by these animals in biocenoses, their distribution, population density, the fact that this species cohabitates with humans, and the insignicant knowledge of their gastrointestinal parasites in India, indicates the necessity of further investigations.

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