Instituto Valenciano de Microbiología

Masía El Romeral
Ctra. de Bétera a San Antonio Km. 0.3
46117 Bétera (Valencia)
Phone. 96 169 17 02
Fax 96 169 16 37
CIF B-96337217

Angullicola crassus  - Molecular diagnosis (PCR); Molecular identification (PCR and sequencing)
Information 24-07-2014.

Angullicola crassus (Angulliculoides crassus) is a parasitic nematode that when adult lives in the swim bladder of eels (Anguilla spp.). This helminth is easily spread in the eel population when it enters a body of water. Its natural host is the Japanese eel (Anguilla japonica). In Europe probably it was introduced with imported eels Southeast Asia, possibly in Taiwan in 1980. In a few years high infestation rates were achieved in the European eel (Anguilla anguilla) existing descriptions of their discovery in Germany and Italy (1982) Denmark (1986), Sweden (1987), Austria (1987), Norway (1983), Latvia (1988) and Spain (1987), among others. Once introduced into a river or lake, it can quickly spread to the eel population, thanks to the high reproduction rate and the low specificity of intermediate hosts, so it is considered one of the dangers to native eels. The introduction of this parasitism in native eel or eel farms, occurs as a result of introducing infected eel, the spread of infected paratenic hosts (eg certain species of parasitized fish), water changes introducing water containing larvae, the introduction of microscopic crustaceans (copepods) parasitized, as can occur with the release of water ballast tanks of ships, etc.

In adult females, once fertilized, being ovoviviparous, the eggs hatch inside the females, and they release phase 1 (L1) larvae in the swim bladder. In this bladder larva they move to stage 2 (L2). This instar passes from the swim bladder to the pharynx, and from this reaches the digestive tract, being eliminated with the feces of eels. Once the larvae phase 2 (L2) reach the water, found in it and in the sediment, where they can survive long in fresh water, and somewhat less in salt water. This larva phase 2 (L2) can be ingested by the usual intermediate host, or some paratenic host, where the larval stage 3 (L3) will result. Their hosts usual intermediaries are several species of small crustaceans (copepods). In these intermediate hosts mature to reach phase 3 of larve (L3). The intermediate host is ingested by eels, and migrate from the digestive tract to reach the air bladder, which lead to stage 4 larvae (L4), which mature into adults. Other insects, mollusks, amphibians, fish, etc., living organisms can act as paratenic hosts.

The diffusive factors are: long survival larval stages free, high fertility, high reproduction rate and responsiveness of various host.
Infected eel, due to the presence of larvae and / or adults suffer a chronic inflammation of the air bladder, which can present hemorrhages, areas of necrosis, collapse and secondary infections, becoming swimbladder a nonfunctional tissue mass, which then causes decreased growth and increased mortality. Altering the swimbladder affects retrograde migration to their breeding grounds, affecting natural eel population. This involvement depends on the intensity of parasitism. Heavily infected eels are at greater risk of being caught by predators, such as cormorants. In eel breeding farms, it causes a reduction in the growth rate, which can lead to mortality, and consequently creates an economic problem.

As control measures proposed control input infected islands fish, water filtration to prevent the penetration of host parasitized intermediaries, and treatment of the water used for crops with certain products such as levamisole, metrifonate, flumequine, oxytetracycline . Some of these treatments are not practical at cost and the need for repeated application. An alternative that has been considered is increasing salinity for the larvae phase 2 (L2) decrease survival.

Tests in IVAMI:

  • Eels: detection of adult and / or larval swimbladder by dissection, macroscopic and microscopic observation, and molecular identification confirmation by sequencing the gene citocromoxidadasa 1 (CO1).
  • In separate water by filtration copepods: detection parasitación larvae stage 3 (L3), by microscopic observation and confirmation by molecular identification by sequencing the gene citocromoxidadasa 1 (CO1).
  • In paratenic hosts (eg Pseudorasbora parva or other..): Detection of larval stage 3 (L3), by microscopic observation of enzyme digested tissues, and molecular identification by sequencing the gene citocromoxidadasa 1 (CO1).

Delivery of results

It will be approximately fifteen days from receipt of the sample in our laboratory. If we have before it would communicate the results.

Preservation and shipment of sample:

Refrigerated (preferred) for less than 2 days.
Frozen: over 2 days.

Cost of testing: consult