Metastrongyles of Pigs
Only one genus occurs in pigs, Metastrongylus, and it is exceptional in having earthworms, rather than mol­luscs, as intermediate hosts.

Identification
  • Slender white worms, up to 6.0 cm in length
  • the host, site and long slender form are sufficient for generic identification.
  • The eggs have rough, thick shells, and are larvated when laid (Ovo-viviparous).
Image result for parasitologyEpidemiology
  • Metastrongylosis shows a characteristic age distribu­tion, being most prevalent in pigs of 4-6 months old.
  • The parasite is common in most the countries although outbreaks of disease do not often occur, probably due to the fact that most systems of pig husbandry do not allow ready access to earthworms by pigs.
  • Though it is often suggested that Metastrongylus may transmit some of the porcine viruses, and may enhance the effect of pathogens already present in the lungs, the role of the worm is not conclusively proven
Life Cycle
Eggs hatch almost immediately, the intermediate host ingesting the L1

 


In the earthworm, development to L3 takes about ten days at optimal temperatures of 22-26 °C.

The pig is infected by ingestion of earthworms

the L3 released by digestion, travel to the mesenteric lymph nodes and moult to L4

Then, L4 reach to the lungs by the lymphatic-vascular route

the final moult occurred after arrival in the air passages.

Female lay eggs which are swallowed and passed in the feces
PPP: 4wks
Note:
  • In cold temperatures the eggs are very resistant and can survive for over a year in soil
  • The longevity of the L3 in the earthworm is similar to that of the intermediate host itself, and may be up to seven years.

Pathogenesis
  • During the prepatent period areas of pulmonary con­solidation, bronchial muscular hypertrophy, and peribronchial lymphoid hyperplasia develop often accompanied by areas of overinflation.
  • When the worms are mature, and eggs are aspirated into the smaller air passages and parenchyma, consoli­dation increases and emphysema is more marked
  •   About six weeks after infection, chronic bronchitis and emphysema are established and small greyish nodules may be found in the posterior part of the diaphragmatic lobes; these may aggregate to form larger areas and are slow to resolve.
  • Purulent staphylococcal infection in the lungs has been noted in many cases of metastrongylosis



Clinical Signs
Most infections are light and asymptomatic. However in heavy infections
  • coughing accom­panied by dyspnoea and nasal discharge.
  • Secondary bacterial infection may complicate the signs.
Diagnosis
  • Clinical History
  • Clinical signs
  • Coproscopy:
    • Flotation is recommended along with the use of magnesium sulphate because of the heavy density of the eggs.
    • The small rough-shelled larvated eggs are characteristic, but it should be recollected that Metastrongylus is often present in nor­mal pigs.
Treatment
·         Many anthelmintics including the modern benzi-midazoles, levamisole and the avermectins/milbe-mycins are highly effective.
Control
·         When pig husbandry is based on pasture, control is extremely difficult because of the ubiquity and longev­ity of the earthworm (intermediate host).
·         On farms where severe outbreaks have occurred pigs should be housed, dosed, and the infected pasture should be cultivated or grazed with other stock.


Related Posts:

  • Male reproductive organ of nematode, Male genital organ: 1. One or Two tubular testis 2. vas deference 3. Seminal vesicle 4. An ejaculatory duct Accessory structure:  (important for identification of … Read More
  • Special Note on Ringworm The term ringworm or ringworms refers to fungal infections that are on the surface of the skin. The name is derived from the early belief that the infection was due to a worm, which it is not. Ringworm is a fungal infectio… Read More
  • Species, life cycle, Identification, pathogenesis, treatment & control of Cooperia Cooperia ·         In temperate areas, members of the genus Cooperia usually play a secondary role in the pathogenesis of parasitic gastroenteritis of ruminants. ·   … Read More
  • Female genital system of nematode Female genital organs: Two ovaries Two oviduct (here fertilization of ovum takes place) Two uterus (unite in receptaculum seminis) receptaculum seminis Vagina Vulva: vulva opens in various position on the … Read More
  • Digestive system of nematode Digestive System: Ø  Complete digestive system Ø  It is a long, straight tube extends from the Mouth to Anus and floats in the fluid filled body cavity. Ø  On cross section, the digestive tract resembles … Read More

0 Comments:

Powered by Blogger.

Visitors

198237
Print Friendly Version of this pagePrint Get a PDF version of this webpagePDF


 download University Notes apps for android

Popular Posts

Flag Counter