Important Parasitic Diseases and Their Prevention in Swine
Jai Bhagwan1, Mahavir Chaudhari2, Hardeep Kalkal3
1Assistant Professor, 2 Extension Specialist, Pashu Vigyan Kendra, Sirsa, Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, 3 Extension Specialist, Krishi Vigyan Kendra, Sirsa (CCS HAU Hisar)
India has the largest cattle resources in the world, which is essential to the economy and way of life of rural people. Pigs are one of the most prolific and quickly developing livestock species, and they hold a significant position because they are raised by economically and socially disadvantaged populations. Pigs have a greater potential than other livestock species to provide farmers with an easy and quick financial return because of their intrinsic characteristics including high production, superior feed conversion efficiency, early maturity, and short generation intervals. In India, most of the pig farmers prefer backyard farming. Pigs are let loose to feed in garbage dumps during the day time, thus they may expose to a variety of pathogens including parasites. Such pigs harbouring zoonotic parasites, can act as potential source of human health hazards. In addition, swine parasites lead to economic losses due to condemnation of liver, decrease in carcass yield and feed conversion. There are various studies reported presence of nematodes (Ascaris spp., Trichuris spp., Strongyle spp., Strongyloides spp.) and protozoa (Isospora spp., Eimeria spp., Cryptosporidium spp., and Giardia spp.) in pigs.
These parasites must use nutrients from the host to multiply and survive. They are found in the digestive tract, the kidneys, liver, lungs or the blood stream. The sow becomes the source of potential infection to piglets. The threadworm (Strongyloides ransomi) is important in the piglet. The life cycles of all are direct from eggs in faeces to adult in the intestine.
1. Roundworms
Most hogs have Ascaris infections during their lifetimes. These roundworms are usually found in greatest numbers in pigs up to 2 to 3 months of age with a few in older pigs. Sows usually are not clinically affected, but serve as carriers. Roundworms are long (6 to 12 inches), stout, pinkish worms, sometimes with curved tails. The adults live in the small intestine, grazing on the gut lining and ingesting particulate and liquid materials from digesting food.
Several clinical events may occur in the infected pig. They include:
- Inflammation of the liver due to an allergic reaction to ascarid larva migration.
- “Milk spots” on the liver that usually disappear with time.
- Another allergic reaction occurs in the lungs as larvae move through the air spaces.
- The lung tissue becomes thick and wet, leading to inefficient respiration and “thumps.” This process is made worse by dust, ammonia and bacteria.
- Colic or gut pain may result from worms in the small intestine grazing or nipping forcefully on the gut lining and stretching the gut wall as the worms grow.
- An impaction and even tearing of the gut may occur.
- Often most obvious to the producer is competition of the pig and its roundworm burden for nutrients, so that wormy pigs are set back and appear unthrifty.
- Otherwise healthy pigs with a low worm burden may appear normal, but performance as judged by feed conversion may be depressed.
Treatment and control of roundworms
- Infected pigs are easily treated by dosing with a suitable treatment, e.g. piperazine. The pregnant sow should be treated before giving birth or she will pass on infection to her litter. One female worm will produce a million eggs a day which pass out in the dung. These eggs infect new hosts and can stay in the ground or the pigsty for up to 5 years.
2. Whipworms
The whipworm Trichuris suis is slender, 2 to 2-1/2 inches long, and found in the caecum and upper large intestine. The slender head end of this small worm penetrates the gut lining, causing irritation and some blood loss. Females worms sporadically produce microscopic eggs in pigs 3 months of age and older. Eggs are infective and capable of surviving long periods in soil or on dirt- and feces-covered slatted and concrete floors. When pigs ingest eggs, infections remain in the intestinal tract of the pig and larvae do not migrate. There is a period of three months from the time of infection to passing eggs; bloody scouring may occur during this period as well as during egg production.
3. Kidney worms
The kidneyworm, Stephanurus, is a short (1 inch), stout, black and white worm found in the fat around the kidney and sometimes in the kidney. Mature infections are found primarily in sows, since it takes nine months to one year after infection before eggs are produced by adult kidney worms. Because infection occurs in and around the kidneys, eggs are passed in the urine.
Wooded lots and shaded farrowing pens often become contaminated areas where larvae hatch from eggs and enter the soil. Pigs may become exposed to infective larvae by ingestion, skin penetration and ingestion of infected earthworms. Larvae then move from the small intestine and eventually into the liver, where they remain for two to four months. Other organs such as the lungs and spleen may also be infected.
4. Coccidia
Neonatal (baby pigs) coccidiosis caused by Isospora suis is found wherever pigs are raised in confinement. Clinical signs of yellowish or gray pasty to liquid diarrhea appear at 1 to 2 weeks of age with dehydration evident even though nursing continues. Infection occurs in cells lining the small intestine. Oocysts (microscopic egglike forms) are passed five days after infection. Oocysts mature in 12 hours in the farrowing crate, and disease and mortality are directly proportional to the number of infective oocysts ingested. There has been no good evidence that sows are carriers and pass oocysts to their piglets. The source for this coccidian is still not known.
The other coccidia, Eimeria, which are found in weanling and older pigs, apparently cause little or no damage. Differentiation of Isospora from Eimeria can be made microscopically by the veterinarian but coccidiosis in baby pigs is apparently Isospora only. Unfortunately, none of the anticoccidial drugs is effective against Isospora, but sanitation of farrowing crates by thorough cleansing can be successful in its control. Control is best achieved by:
- Thorough cleaning and sanitation between each farrowing
- Monitoring of movement of personnel and supplies
- Control of pests and rodents to reduce mechanical transmission of the oocysts.
Causes or factors responsible for parasitic infestation
- Management systems that allow regular access to faeces.
- Faeces allowed to accumulate for more than 3 – 4 days (allows eggs to become infective).
- Moist wet areas encourage survival of eggs.
- No all-in, all-out management.
- Permanently populated yards or paddocks outdoors.
- Failure to monitor faeces for egg output.
- Failure to carry out routine treatments when indicated.
- Continuously used pens increase the risks of infection.
- Wet dirty floors.
- Carrier pigs.
Control and prevention of parasites
Controlling parasites requires an understanding of their life cycle. Procedures can then be adopted that together with anthelmintics, break this cycle and thus prevent re-infection. Parasite control should include good sanitation. Good nutrition is critical to the pig’s ability to mount an immune response and maintain performance in the presence of parasites. Since roundworms and whipworms have transmissible eggs, indoor facilities need to be well-cleaned and traffic minimized. Gilts should be kept off of contaminated lots, and weaned pigs kept away from older breeding stock. When dry lots, pastures and wooded areas are used for hog production, prevention is chiefly by treatment, but changing sites away from contaminated areas may help. Unfortunately, roundworm and whipworm eggs persist for long periods, kidneyworm and lungworm larvae are found in earthworms, and Strongyloides may be passed in colostrum. Management can be improved by calling of extension specialist or veterinarian.
Diagnosis
This is based on symptoms and identification of the parasites. Laboratory examination of faeces for worm eggs.
