PARASITOLOGI

Gnathostoma spinigerum

1.1 Klasifikasi

Kingdom: Animalia

Phylum: Nematoda

Class: Secernentea

Order: Spirurida

Family: Gnathostomatidae

Genus: Gnathostoma

Species: Gnathostoma spinigerum

1.2Distribusi Geografis

            Thailand, Vietnam, India, Malaysia, Indonesia, Jepang, Philiphina, Tiongkok.

1.3 Penyakit

Gnathostomiasis

1.4 Habitat

            Cacing dewasa yang hidup di dalam benjolan dinding usus mamalia pemakan ikan.

1.5 Morfologi

Cacing dewasa panjangnya bervariasi; jantan : 11-25 milimeter, betina : 25-54 milimeter. Mempunyai 3 stadium larva. Manusia dapat terinfektir oleh larva stadium 3 yang bentuknya serupa dengan dewasa, kepala membulat, pada bagian kepala dikelilingi oleh 4 baris kait yang melingkar (seperti ring).

Morphology:

a. The adult parasite is reddish-brown in color and has a globular cephalic dome that is separated from the rest of the body by constriction

b. The posterior portion of the nematode is smooth while the anterior half is covered with fine leaf-like spines

c. The head is round and contains 4 to 8 transverse rows of hooklets that are protected by a pair of fleshy lips

d. The males are shorter than the females, 11 to 25 mm compared to 25 to 54 mm respectively

e. Eggs are usually yellow or brown, oval, and have a mucoid plug at one end

f. The third stave larva is the infective form of this parasite and can be identified by its round extremes and cylindrical body as well as the rows of cuticular spines that decrease towards the posterior end

g. The number of hooklets present on the advanced third stage larvae is used in the identification of the parasite when removed from a patient

 

1.6 Siklus Hidup

Life Cycle in Definitive Hosts of Gnathostomiasis

a. Adult worms found in a tumor located in the gastric wall of the definitive hosts and release eggs into the host’s digestive tract.

b.  The eggs are then released with feces and in about a week hatch in water to develop into the first larva stage.

c. Larvae are then ingested by minute copepods of the genus Cyclops.

d.  Once entering the copepod, the larva penetrate the gastric wall of their intermediate host and begin to develop into second-stage and even early third-stage larva.

e. The copepods are then ingested by a second intermediate host such as fish, frogs, or snakes.

f. Within this second intermediate the larva repeat a similar pattern of penetrating the gastric wall, but then continue to migrate to muscular tissue and develop into advanced third-stage larvae.

g.  These larvae then encyst within the musculature of the new host.

h.  If the cyst containing flesh of these hosts is ingested by a definitive host, such as tigers, the cysts are ingested and the larvae escape the cysts and penetrate the gastric wall.

i.   These released larvae travel to the connective tissue and muscle as observed before and after 4 weeks they return to the gastric wall as adults.

j.   Here they form a tumor and continue to mature into adults for the next 6-8 months.  Worms mate and begin to excrete eggs with feces 8-12 months after ingestion of cysts.

Life Cycle in Humans

a.  Infection in humans follows ingestion of raw, insufficiently cooked infected intermediate hosts.

b.  The ingested third stage larvae migrate from the gastric wall and its migration through subcutaneous tissues results in the symptoms associated with gnathostomiasis infection.

c.  The third stage larvae do not return to the gastric wall, which prevents the larvae from maturing into adult worms, leaving the parasite unable to complete its life cycle.

d.  Instead the larvae continue to migrate unpredictably in the patient, and are unable to develop into adults, so eggs are seldom found in diagnostic tests.

e.  This also means the number of larvae present in humans is a reflection of the number of third stage larvae ingested. 

a. Gnathostoma spinigerum dewasa tinggal pada tumor dinding usus dari kucing atau anjing.

b. Telur dikeluarkan oleh cacing dewasa dari tempat lesi tersebut yang kemudian keluar bersamafaeces masuk kedalam air. Didalam air telur berkembang menjadi embryonated yang kemudianmenetas keluar larva stadium I.

c.  Larva stadium I bergerak bebas di dalam air dan bila tertelan oleh intermediate host I (cyclops)maka di dalam tubuh cyclops berkembang menjadi larva stadium II.

d. Bila cyclops tersebut dimakan oleh Intermediate Host II (ikan, katak atau ular) maka larva stadium II akan berkembang menjadi larva stadium III dalam tubuh binatang-binatang tersebut.

e. Bila Intermediate host II dimakan oleh Definitif host maka larva akan tumbuh menjadi cacing dewasa. Manusia terinfektir bila makan Intermediate host II yang kurang sempurna memasaknya. Tetapi dalam tubuh manusia tak dapat berkembang menjadi dewasa (tetap stadium III)dan mengadakan migrasi.

1.7 Mekanisme Transmisi

            Gnathostomiasis is primarily transmitted by ingestion of raw, insufficiently cooked intermediate hosts such as fresh water fish, birds or amphibians. There have also been reports of transmission by direct penetration of the skin on the palm resulting from the handling of infected meat.  Mother to fetus transmission has also been identified as a result of larva migration to the fetus through the placenta.

 1.8 Sumber Infeksi

1. Intermediate host

The primary intermediate host for gnathostomiasis is the minute crustacean of the genus Cyclops.  These crustaceans are then ingested by a second intermediate host such as fish, birds, and frogs. 

            2. Definitive host

The definitive host for gnathostomiasis includes cats, dogs, tigers, leopards, lions, minks, opossums, and raccoons.  However the primary reservoirs for this parasite are cats and dogs.

1.9 Incubation Period

            The incubation period for gnathostomiasis is 3-4 weeks which is when the larvae begin to migrate through the subcutaneous tissue of the body.

1.10 Patologi dan Simtomatologi

            Di dalam hospes alami seekor cacing atau lebih terdapat di dalam benjolan dengan indurasi di dalam dinding perut atau kadang-kadang di dinding usus. Pada manusia cacing yang belum dewasa dapat ditemukan di dalam alat-alat dalam atau dekat kulit. Pada tempat-tempat tersebut mereka membentuk pembengkakan dan abses yang meradang yang mungkin menetap atau cepat hilang. Cacing dapat berpindah-pindah melalui jaringan hospes dan membuat terowongan mendatar melalui jaringan kulit, membentuk semacam “creeping eruption”. Invasi mata disertai dengan iritis, uveitis, perdarahan dan cellulitis orbita pernah dilaporkan. Saluran nekrosis dengan perdarahan yang berat ditimbulkan oleh perpindahan cacing melalui sumsum tulang dan otak. Diantara gejala dan keluhan yang timbul karena peradangan setempat terdapat eosinofili, hematuri, hemoptysis, pembengkakan pharinx dengan sesak napas, dan edema angioneurotik dan abses.

 1.11 Diagnosis

            The primary form of diagnosis of gnathostomiasis is the identification of larva in the tissue.  Serological testing such as enzyme-linked immunosorbent assay (ELISA) or the Western blot are also reliable but may not be easily accessible in endemic areas.  CT scan can be used to help identify a soft tissue worm and when looking at CNS disease it can be used to reveal the presence of the worm.  Urinalysis can also be used to identify the presence of hematuria or the worm, but it is not a very reliable diagnostic tool.

            Pembengkakan subkutis, eosinofili yang nyata dan penderita berada di suatu daerah endemi memberikan kemungkinan infeksi, tetapi diagnosis akhir tergantung kepada identifikasi cacing. Reaksi intrakutan telah pula dipakai.

 1.12 Pencegahan

The best strategies for preventing accidental infection of humans education of those living in endemic areas is to educate those living in endemic areas about the risk associated with eating raw seafood.  The inability of the parasite to complete its life cycle within humans means that transmission can easily be contained by adequate preparation of meat from intermediate hosts.  This is especially useful because of the difficulty and lack of feasibility inherent in eliminating all intermediate hosts.  So instead, individuals in endemic areas should avoid eating raw and undercooked meat in endemic areas, but this may be difficult in these areas.  This is due to the preference for dishes containing raw fish in these endemic areas.  The dish ceviche is native to Peru and is a favorite of Mexico.  It consists of onion, cubed fish, lime or lemon juice, and Andean spices including salt and chili.  These ingredients are mixed together and are allowed to marinate for several hours before being served at room temperature.  Then in endemic areas in Southeast Asia there are traditional dishes that contain raw seafood that are also associated with these endemic areas, such as koipla in Thailand, koi ga in Vietnam, and sushi in Japan.  By acknowledging these cultural traditions, education can be tailored to these cultures and individuals can be educated on methods of adapting their food preparation activities in order to remove the larvae without greatly altering these traditional dishes.  For instance, meat should be marinated in vinegar for six hours or in soy sauce for 12 hours in order to successfully kill the larvae.  In areas with reliable electricity, meat can be frozen at -20 degrees centigrade for 3-5 days to achieve the same results of killing the larvae present.    

1.13 Pengobatan

The most prescribed treatment for gnathostomiasis is surgical removal of the larvae but this is only effective when the worms are located in an accessible location.  In addition to surgical excision, albendazole and ivermectin have been noted in their ability to eliminate the parasite.  Albendazole is recommended to be administered at 400mg daily for 21 days as an adjunct to surgical excision, while ivermectin is better tolerated as a single dose.  Ivermectin can also serve as a replacement for those that can’t handle albendazole 200 ug/kg p.o. as a single dose.  However, ivermectin has been shown to be less effective then albendazole .