Food Borne Parasites and their control

1. WEST BENGAL UNIVERSITY OF ANIMAL & FISHERY SCIENCES
FACULTY OF FISHERY SCIENCES
A Seminar on
Food borne parasites and
their control
Submitted To:
Prof. T. J. Abraham
(Dept. of AAH) Submitted By:
Ratul Chakraborty
FS-19/14
B.F.Sc. 3rd Yr. 2nd Sem
Course: AAH-323

2. Introduction
– The presence of parasites in fish is very common, but most of them are of little
concern with regard to economics or public health.
– More than 50 species of helminth parasites from fish and shellfish are known to
cause disease in human beings.
– All parasitic helminths have complicated life cycles. They do not spread directly
from fish to fish, but must pass through a number of intermediate hosts in their
development process.
– Most of the parasites are rare and involve only slight to moderate injury, but some
pose serious potential health risks.
– Very often sea snails or crustaceans are involved as the first intermediate host and
marine fishes as the second intermediate host, while the sexually mature parasites are
found in the mammals as the final host.
– Infection of human may be a part of this life cycle or it may be a side track causing
disruption of the life cycle.

3. Food Borne Parasites
Nematodes or round
worms
—Aniskis simplex (found in
herrings)
—Pseudoterranova dicipens
(found in cod)
—Gnasthostoma sp. (found in
freshwater fishes and frogs)
—Capillaria sp. (found in
freshwater fishes)
—Angiostrongylus sp. (found
in freshwater prawns, snails,
fish)
Cestodes or Tape worms
—Diphyllobothrium latum
(found in freshwater fish)
—Diphyllobothrium
pacificum (found in sea
water fishes in Peru, Chile
and Japan)
Trematodes or flukes
—Clonorchis sp. (found in the
freshwater fishes of Asia)
—Opisthorchis sp. (found in
the freshwater fishes of
Asia)
—Metagonimus yokagawai
—Paragonimus sp. (found in
the snails, crustaceans and
fishes of Asia, America,
Africa)

4. • Round worms or nematodes are common and found in marine fish all over the world.
• They are typically round worms, 1-6 cms long. If ingested by humans, they may penetrate into the wall of the
gastro-intestinal tract and cause acute inflammation (also known as ‘herring worm disease’).
• Upon ingestion, the larvae may migrate to various regions most commonly to the subcutaneous sites on thorax,
arms, head and neck where the worms induce a creeping sensation and edema.
• Infection in human causes severe diarrhea and possible death attributed to fluid loss.
• Sexually dioecious nematodes mate and produce eggs that pass with the faeces or hatch in the intestine.
• Another nematode of health importance is Capillaria sp. The adult worms are gut parasites in piscivorous birds
and intermediate hosts are small freshwater fishes. Infection in humans causes severe diarrhea and possible
death due to excessive fluid loss.
• Angiostrongylus cantonensis adult worms are found in the lungs of rats and the intermediate hosts are snails,
freshwater prawns and land crabs. Can cause meningitis in humans.
Nematodes

5. Anisakis simplex:
1. Anisakis is a genus of parasitic nematodes, which have life cycles involving fish and marine mammals. They
are infective to humans and cause anisakiasis.
2. Anisakis species have complex life cycles which pass through a number of hosts through the course of their
lives.
 Eggs hatch in seawater, and larvae are eaten by crustaceans, usually euphausids.
 The infected crustacean is subsequently eaten by a fish or squid, and the nematode burrows into the wall
of the gut and encysts in a protective coat, usually on the outside of the visceral organs, but occasionally
in the muscle or beneath the skin.
 The life cycle is completed when an infected fish is eaten by a marine mammal. The nematode exists in
the intestine, feeds, grows, mates and releases eggs into the seawater in the host's faeces.
3. Vermiform body plan, round in cross section and a lack of segmentation. The mouth is located anteriorly, and
surrounded by projections used in feeding and sensation, with the anus slightly offset from the posterior.
4. Symptoms: Within a few hours of ingestion, the parasitic worm tries to burrow though the intestinal wall, but
since it cannot penetrate it, it gets stuck and dies. The presence of the parasite triggers an immune response;
immune cells surround the worms, forming a ball-like structure that can block the digestive system, causing
severe abdominal pain, malnutrition and vomiting. Occasionally, the larvae are regurgitated. If the larvae pass
into the bowel or large intestine, a severe eosinophilic granulomatous response may also occur one to two weeks
following infection, causing symptoms mimicking Crohn's disease.

6. Treatment Information
It is often possible to diagnose and treat gastric anisakiasis by
removal of the worm using an endoscope. Diagnosis of enteric anisakiasis is more
difficult; however, it can generally be managed without removal of the worm
because the worm will eventually die. Surgery may be required for intestinal or
extra-intestinal infections when intestinal obstruction, appendicitis, or peritonitis
occurs. Successful treatment of anisakiasis with albendazole @ 400 mg orally twice
daily for 6 to 21 days has been reported in cases with presumptive diagnoses.
Albendazole
Oral albendazole is available for human use in the United States.
Caused due to:
The transmission of these food-borne pathogens is particularly
associated with traditions of consumption of raw or undercooked fish. A number of
fish dishes are considered to be high risk for the contraction of anisakidosis,
including Japanese sushi and sashimi, Filipino bagoong, Dutch salted or smoked
herring, etc. The preparation of these dishes may involve methods (salting, curing,
marinating, pickling, and smoking at 40°C, etc.) which are generally sterilizing for
other food-borne pathogens but not for anisakids.

7. Anisakis simplex
Anisakid larvae in the body cavity
of herring (Clupea herring)

8. Angiostrongylus cantonensis
1. Angiostrongylus cantonensis is a parasitic nematode (roundworm) that
causes angiostrongyliasis, the most common cause of eosinophilic
meningitis in Southeast Asia and the Pacific Basin.
2. The nematode commonly resides in the pulmonary arteries of rats, giving it the
common name rat lungworm. Snails are the primary intermediate hosts, where larvae
develop until they are infective.
3. Humans are incidental hosts of this roundworm, and may become infected through
ingestion of larvae in raw or undercooked snails or other vectors, or from
contaminated water and vegetables. The larvae are then transported via the blood to
the central nervous system (CNS), where they are the most common cause
of eosinophilic meningitis, a serious condition that can lead to death or permanent
brain and nerve damage
Transmission: Transmission of the parasite is usually from eating raw or undercooked
snails or other vectors. Infection also occurs from ingestion of contaminated water or
unwashed salad that may contain small snail and slugs or have been contaminated by
them.

9. Management and therapy: Treatment of Angiostrongylus sp. is not well defined,
but most strategies include a combination of anti-parasitics to kill the worms.
1. Anti-helminthics: Anti-helminthics are often used to kill off the worms.
Mainly albendazole, ivermectin, etc are used.
2. Anti-inflammatories: Anti-helminthics should generally be paired with
cortico-steroids in severe infections to limit the inflammatory reaction to the
dying parasites.
3. Symptomatic treatment: Symptomatic treatment is indicated for symptoms
such as nausea, vomiting, headache and in some cases chronic pain due to
nerve damage or muscular atrophy.
Prevention:
1. Aviod consumption of uncooked vectors, such as snails and freshwater prawns.
2. Avoid drinking water from open sources, which may have been contaminated
by vectors

10. Angiostrongylus cantonensis

11. Cestodes or Tape-worms
 Only a few cestodes or tapeworms in man are known to be transmitted by fish.
 The broad fish tapeworm Diphyllobothrium latum is a common human parasite reaching up to 10m in
length. Resides in the human intestinal tract.
 The parasite has micro-crustacean as first intermediate host and freshwater fishes as second intermediate
host.
 The cestode is transmitted mainly by the marine fishes.
 Commonly occurs in the coastal regions of Peru, Chile and Japan where raw fish preparations are
common.

12. Diphyllobothrium pacificum
Diphyllobothrium is a genus of tapeworm which can cause diphyllobothriasis in humans through
consumption of raw or undercooked fish.
 Life cycle: The life cycle of Diphyllobothrium pacificum is similar to that od D. latum, with the exception that the
second intermediate hosts are salt water soecies. These include sea lions, raw or under-prepared marine fish infected
with pleroceroid larvae
 Transmission: Human infection is related to the consumption of raw or undercooked fish.
 Disease caused: Diphyllobothriasis is typically an asymptomatic condition, but many symptomatic cases of human
infection go largely unnoticed because of the nonspecific symptoms such as nausea, intestinal discomfort, and
diarrhea.
 Prevention: A combination of improved sanitary surveillance of imported fish (salmon and others) and increased
emphasis on sanitary practices in restaurants appears to be the best strategy for controlling and impeding the
installation of this helminth in Brazil. Other effective control measures include cooking fish properly and freezing
the fish below 20°C for a minimum of 7 days or below 35°C for 15 hrs before ingestion. There is a large number of
possible drugs available to treat this disease, and the two main ones used are niclosamide and praziquantel, both of
which are highly effective. A single dose of praziquantel (600 mg) was given, and was found to be adequate for
curing the patient.

14. Trematodes or flukes
i. Trematodes are also known as flukes. Common in Asia.
ii. Intermediate hosts are snails and freshwater fishes, while dogs, cats and humans are the
final hosts.
iii. The fluke develops in the liver and bile ducts and spreads slowly in the human body.
iv. Reach sexual maturity in the liver of humans. Eggs enter the intestine in the bile, are
incorporated into the faeces for transmission.
v. The larvae penetrate the tissues through morphologically distinct stages, which by asexual
reproduction produces free swimming larvae.
vi. They live in the intestine of the final host, causing inflammation, symptoms of diarrhea and
abdominal pain.

15. Paragonimus sp.
1. Paragonimus is a genus of flukes (trematodes)
2. The first intermediate hosts of Paragonimus is the freshwater snails.
3. Life cycle: The parasite passes through two intermediate hosts, an aquatic snail and a crustacean.
It enters its mammalian definitive hosts when they eat infected freshwater crustaceans. Typical
hosts include dogs, cats, and humans. Humans usually contract paragonimiasis when they eat
undercooked freshwater crabs or crayfish, that contain live metacercariae.
4. Mode of reproduction: In the intestine, the parasite will move into the abdomen and commonly
into the lungs. In the lung, the parasites encyst and cross fertilize each other. The cyst eventually
ruptures in the lungs and the eggs may be coughed up or swallowed and excreted in the feces. An
egg landing in fresh water hatches and releases a ciliated miracidium. A successful miracidium
swims about until it finds an intermediate host, usually an aquatic snail. A crustacean in turn
becomes infected by eating infected snails. The definitive host completes the cycle if it eats
infected crustaceans.

16. 7. Symptoms: Symptoms of paragonimiasis may include abdominal pain, diarrhea, fever, and hives. If the infection remains
untreated, the symptoms may peter out after only few months, but sometimes they last for decades. Paragonimiasis is caused by
the body's natural immune response to the worms and eggs that are present and also migrating from the intestines to the lungs.
As a rule, the parasites begin to cause the symptoms about three weeks after ingesting them in live condition. Some patients
develop brain damage if parasites establish in the brain and produce eggs. The brain damage commonly
causes headache, vomiting, and seizures. Untreated cerebral paragonimaisis commonly results in death from increased intra-
cranial pressure.
8. Treatment: Praziquantel has been used to effectively treat paragonimiasis by separating the tegument. An effectively
complete rate of cure may be expected after three days of treatment if there has not been too much permanent damage, such as
from intracranial effects. Other medications can also be used such as bithionol, niclofan, and triclabendazole with high cure
rates.
9. Prevention: Thorough cooking of an infected crustacean kills all stages of the parasite. Crab meat should not be eaten raw,
even if pickled, because the pickling solution often fails to kill all the parasites. Utensils and cutlery boards should be cleaned
thoroughly before and after food preparation.

18. Metagonimus yokogawai
1. Metagonimus yokogawai is a species of a trematode, or fluke worm, in the family Heterophyidae.
2. It is a human parasite causing metagonimiasis.
3. Distribution: This species occurs in Korea, China, Taiwan, Japan, Russia, Indonesia, Israel, and Spain.
4. Life cycle: The first intermediate hosts of Metagonimus yokogawai include freshwater snails. The second intermediate
host include freshwater fish. Natural definitive hosts are: dogs, cats, rats, and humans.
5. Reproduction: All the species are hermaphroditic and capable of self-fertilization.
6. Clinical Presentation: The main symptoms are diarrhea and colicky abdominal pain. Migration of the eggs to extra-
intestinal sites (heart, brain) can occur, with resulting symptoms.
7. Treatment: Praziquantel is recommended in both adult and pediatric cases with dosages of 75 mg/kg/d in 3 doses for 1
day. Possible side effects include abdominal pain, allergy, diarrhea, headache, hepatic
dysfunction/hepatitis, nausea or vomiting,, rash, somnolence, vertigo or dizziness. Another possible drug option
is Tetrachloroethylene, a chlorinated hydrocarbon, but its use has been superseded by new antihelminthic drugs (like
Praziquantel).

19. Metagonimus yokogawai

20. Control of diseases caused by parasites
1. Avoidance of capture of nematode infected fish by selecting specific fishing
grounds.
2. Sorting and removal of nematode infected fish or removal of nematodes from
fish by hand over a candling table.
3. Use marinated fish: Safe processing is primarily based on the level of NaCl in
the tissue fluid. If around 8-9% NaCl is present in the tissue fluid, then the
maximum survival period of the nematodes is found to be 5-6 weeks.
4. Use of frozen fish: freezing to -20 degree centigrade and maintaining this
temperature for atleast 24 hours will kill all nematodes.

21. Conclusion:
Thus from the above seminar topic we have come across several forms of parasites and their harmful effects
on the human health. Therefore in order to keep ourselves healthy and fit, we must remain aware of the parasites and
consume less diseased fish. Discard all the diseased fish will also reduce the contamination level among the other
cultured species.
References:
1. www.google.com/wikipedia
2. Fishery ecourse
3. (Japanese) Katsurada F. (1912). "Heterophyes in Japan. II. Creation of a new
genus Metagonimus". Okayama Igakkai Zasshi 273: 768–778.
4. Shimazu T. & Kino H. (2015). "Metagonimus yokogawai (Trematoda: Heterophyidae): From
Discovery to Designation of a Neotype". The Korean Journal of Parasitology 53(5): 627-
639. doi:10.3347/kjp.2015.53.5.627.
5. Chai J. Y., Darwin Murrell K. & Lymbery A. J. (2005). "Fish-borne parasitic zoonoses: Status and
issues". International Journal for Parasitology 35(11-12): 1233-
1254. doi:10.1016/j.ijpara.2005.07.013http://www.dpd.cdc.gov/DPDx/HTML/Angiostrongyliasis.html
http://www.dpd.cdc.gov/DPDx/HTML/ImageLibrary/Angiostrongyliasis_il.html
http://www.cdc.gov/ncidod/dpd/parasites/angiostronglus/factsht_angiostrongylus.html
http://animaldiversity.ummz.umich.edu/site/accounts/information/Angiostrongylus_cantonensis.html