Coccidiosis affects all ages of pigs and is a tacky or watery diarrhoea, piglets do not seem to grow very well and can cause death in piglets. It stems from poor hygiene.

Causes

Coccidia are single cell protozoan parasites which multiply in the cells lining the intestine. Cystoisospora suis is the main pathogen of piglets and is responsible for the most coccidial diarrhoea. Cryptosporidium parvum, C. suis and other genotypes may also affect piglets but occurs commonly in weaned pigs and Eimeria species occur in weaned pigs, finishers and gilts but not in piglets. The resistant oocysts of Cystoisospora. suis are eaten and reach the upper small intestine where small sporozoites hatch and invade cells of the intestinal lining within 24 hours. They multiply asexually, damaging their host cell, to give rise to first stage merozoites and then to a further two stages within cells of the small intestinal lining. Each fourth stage cell reaches the lower part of the small intestine at about 4-5 days after infection and invades an epithelial (lining) cell to produce the sexual stage. Some become groups of microgametes and some remain single to become macrogametes. Mating in the gut produces oocysts which appear in the faeces as oocysts within 5 days of infection. Eimeria species multiply in the same way as C. suis, but Cryptosporidium remains in the absorptive, apical part of the cell and appears to prevent absorption of nutrients and causes cell death.

Transmission

Coccidia are passed out in the faeces and Cystoisospora suis oocysts develop within 48 hours at 24-27ºC into resistant hard walled sporulated oocysts which are infective. They are resistant to drying and can persist in piggeries and soil for up to 10 months. The major source of infective oocysts is the faeces of piglets aged between 2 and 4 weeks, when from 4,000 to 400,000 oocysts per gram may be present. Sows may pass a few oocysts and infect their litters, but the major source of both direct and indirect infection is the piglet. Transmission of Eimeria species resembles that of Cystoisospora, although the age range affected differ, but some Cryptosporidium species have more than one host species. The route of infection is oral in all cases.

Signs

Coccidiosis causes mal-absorption, diarrhoea, loss of condition and some deaths. The faeces of affected piglets may be whitish and firm, there may be transient pasty diarrhoea or profuse yellowish, watery diarrhoea between 5-15 days of age and most commonly from 7-10 days of age. Affected piglets may be thinner than unaffected litter mates and remain gaunt and hairy for some weeks thereafter. Severely affected piglets may die. Mortality rates may reach 20%. The diarrhoea responds poorly to antimicrobial therapy and slow growth occurs in recovered animals and diarrhoea rarely continues beyond weaning. Wasting and diarrhoea have been recorded in gilts, finishing pigs and wild boar infected with Eimeria spp. In experimental E. neodebliecki infection, frothy, mucoid diarrhoea occurred 9-12 days post infection. Most infections with C. parvum are asymptomatic (90% in one study). Clinical signs rarely appear before 3 days of age and are most commonly reported in piglets at 10-21 days of age. Affected piglets are depressed and pass a watery, sometimes brownish, diarrhoea, which may persist for 3-5 days. The organism can be recognised in the faeces of diarrhoeic weaners. Affected weaned pigs are often depressed and anorexic, in poor condition with a rough dirty coat and pasty faeces.

Treatment and prevention

Coccidiosis in piglets can be treated with trimethoprim sulphonamide and they should be supported with electrolyte. Toltrazuril given as an oral suspension by stomach tube on day 3 prevents diarrhoea, prevents oocyst shedding and can maintain piglet growth. Scrupulous attention should be given to hygiene in control, as the high levels of oocysts passed by piglets and their ability to survive for months make environmental contamination important. Sows should be cleaned on entry to the farrowing houses which should be disinfected or fumigated with methyl bromide or ammonia (final concentration 2%). Steam cleaning at 65˚C for 15 minutes and proprietary disinfectants can also be used to destroy oocysts. Less disease and oocyst shedding has been demonstrated on fully slatted cleaned floors. Trimethoprim sulphonamide may be given by injection or orally to older pigs with Eimeria species and the inclusion of an anticoccidial such as amprolium at 1 kg permix per tonne in sow feed for 7-10 days prior to farrowing and for 2 weeks afterwards will reduce the shedding of oocysts by sows and other pigs. No treatment has yet been shown to affect Cryptosporidia. The oocysts can be destroyed by the same disinfectants as those of the other coccidia.

Be aware

Cystoisospora and Eimeria infections are of no public health importance, but the pig may be a source of infection with Cryptosporidium for humans and vice versa.

This affects both gilts and sows and the causes range from mismanagement, fever, infections of the uterus and poisoning.

Effects: The sow/gilt will abort recognisable foetuses before day 110 of gestation, after which production of dead foetuses is classified as a stillbirth. Sows may be visibly ill before abortion occurs or remain normal.

Causes

Death of the conceptuses may occur early from hormonal causes as four live foetuses are required to maintain an early pregnancy. After implantation, infection is the main cause of abortion, indirectly through fever or directly as a result of the infection of the foetus. Fever is the cause of abortion in erysipelas and other feverish diseases. Invasion of the foetus can occur in many viral and bacterial diseases. In some, foetal invasion results in death and dead foetuses reabsorbed, and in older pregnancies, the foetus may become mummified and later stillbirth may occur. All combinations of normal, resorbing, and mummified foetuses may be aborted. Major infections capable of causing abortion are Aujeszky’s Disease, brucellosis, enterovirus infections, leptospirosis, parvovirus, PRRS, swine fever and toxoplasmosis. Ingestion of the mould toxin zearalenone is also capable of causing abortion, as are management factors, such as high carbon monoxide concentrations.

Mode of transmission

Infectious causes of abortion are transmitted by the routes associated with the causal infection. Non-transmissible abortions occur.

Clinical signs

Sows may be seen to abort and the aborted material may be found on the floor of their accommodation. The sow may not appear ill in some cases (enterovirus, parvovirus, some leptospirosis), but in other diseases such as erysipelas, there is clear evidence that the sow is ill, off feed, and has evidence of the disease. In the case of erysipelas, high fever and the characteristic skin lesions are often found. The rectal temperature should be taken to establish the presence of fever. During or after abortion, the vulva may be bloodstained and the tail and hindquarters may be smeared with sticky discharge. As sows frequently eat aborted material, abortion is hardest to detect in loose-housed animals. Where abortion is missed, the termination of pregnancy may be detected only when an animal, previously known to be pregnant, fails to farrow, returns to oestrus or is identified following a pregnancy check. Abortion is recorded in pig herds as a routine. Abortions should be uncommon in a herd (fewer than 1%), but if they reach 2.5%, the cause should be determined. Management factors may be obvious and in zearalenone poisoning, enlargement of the vulvas of piglets and enlargement of the mammary glands in non-pregnant gilts. The presence of specific diseases may only be identified by laboratory examination of the aborted foetuses, vaginal discharges or blood from the affected sow.

Postmortem lesions

The products of abortion may be visible as embryos (large sacs 10-20 cm in length, with a central dark area, the embryo itself, from which blood vessels radiate) or as perfectly formed pig foetuses. These have their eyes closed and are hairless. They may be partially decayed, mummified or perfectly fresh with haemorrhages on their skins. The age of the foetus when death occurred may be determined by measuring foetal crown-rump length. Placentas may be absent, although they are sometimes passed surrounding aborted piglets. Fluid from the chests of aborted foetuses is used to detect infectious agents by culture or PCR and antibody to them may be present after 70 days gestation. Sows are rarely examined postmortem, but ageing corpora lutea are visible in the ovaries and the uterus may be enlarged, although it rapidly returns to normal. Lesions of a causal infectious disease may be visible but laboratory examination of vulva discharge or uterine contents may be required.

Treatment and prevention

The ability to prevent further abortions varies, depending on the cause. For example, zearalenone toxicity can be eliminated rapidly by feeding clean rations. Carbon monoxide poisoning can be eliminated by adjusting gas heaters. Toxoplasmosis may be prevented by stopping contamination of pig feed by cat faeces. Erysipelas can be treated easily with penicillin and leptospirosis with tetracyclines. Solid immunity follows the elimination of these infections. Less specific infections of the uterus can be eliminated, but ideally, the animals should be culled as persisting infection may reduce fertility.

To control abortion, sows can be vaccinated against erysipelas and parvovirus. In some countries, vaccination against leptospirosis, Aujeszky’s Disease, swine fever and PRRS is also possible. Vaccination requires at least 14 days to protect against an agent and may not protect against venereal infections. There are no vaccines for enteroviruses. Brucellosis is notifiable and controlled by other means. The aborted material should be treated as infectious and correctly discarded, with disinfection as appropriate.

Animals which have aborted should come back into oestrus within 10 days and may then be served. The exception is if body condition has been lost when consideration should be given to increasing feed and delaying service. Those that do not return to oestrus or do not hold to the next service, should, unfortunately, be culled.

Special note

Some infectious causes of abortion (Swine Fever, African Swine Fever, Brucellosis) are notifiable and some, such as Brucellosis and Leptospirosis, can infect humans handling the products of abortion. Please ensure that strict hygiene is practised.