Important Pig Diseases and Health Management

Introduction

Pigs are found and raised all over the world, and provide valuable products for humans, including pork, lard, leather, glue, fertilizer and a variety of medicines. India possesses one of the largest livestock wealth in the world and a quarter of the agricultural gross domestic product is contributed by the livestock sector. Among the livestock species, pig finds an important place as it being reared by socio-economically weaker sections of the society. Pig as compared to other livestock species has a great potential to contribute to faster economic return to the farmers, because of certain inherent traits like-high fecundity, better-feed conversion efficiency, early maturity and short generation interval. Pig farming also requires small investment on buildings and management equipment’s. It has immense potential to ensure nutritional and economic security for the weaker sections of the society. In India, 70% of the pig population is reared under traditional small holder, low-input demand driven production system, except for limited number of semi-commercial pig farms in Kerala, Punjab and Goa. The typical production system consists of a simple pigsty and feeding comprises locally available grains, vegetables and agricultural by-products along with kitchen waste. Pork consumption being popular among select populations, improved pig husbandry programmes and pig-based integrated fish farming have significantly contributed in the poverty alleviation strategies of the Government of India.

 Pig keeping and the consumption of pork is increasing and becoming a popular source of livelihoods in rural youths. This is because the demand for pork has increased and the rural and peri-urban communities have discovered the cost-effectiveness of keeping pigs. There is deliberate policy by Government of India to increase pig farming in the rural communities and the ICAR-NRC Pig, Rani, Guwahati is putting a lot of effort into making the pig a viable enterprise. The pig inherently has characteristics that make it thrive under minimum input systems hence providing economic opportunities for rural smallholder pig farmers: (a) the pig is prolific, giving 6-10 viable piglets per farrowing; (b) the pig can grow to slaughter market size within 6 months and (c) the pig is a scavenger and can thrive as a low-input enterprise. Smallholders exploit this scavenger ability to keep pigs in free range conditions.

 Occurrence of diseases causes heavy economic losses in terms of livestock health and production. Advances in animal health are expected to play a major role in the progress of pig production. Control of pig diseases assumes prime importance in the crucial time of shifting of animal agriculture from extensive to intensive and commercial system of management. Presence and accumulation of conventional and newer infectious agents in the environment lead to reduction in quality and quantity of pig production. Strategic control and eradication of economically important pig diseases will result in enhancing pig production in the country. Diseases can cause negative impact and at times make the pig enterprise a very risky economic venture. The development of the pig enterprise will hinge on the following: (a) reliable knowledge about the burden of specific diseases of the pigs, (b) proper knowledge about the predisposing factors for the spread and thriving of particular diseases which is key to mitigations and (c) putting in place proper control practices that can prevent/reduce the occurrence hence the burden of the particular diseases on the pig industry. The aim of present chapter is to have a brief overview on economically important and emerging swine diseases and their management under Indian scenario.

Piglet Mortality

The evolutionary biology of the pig means that it is predisposed to produce more offspring than it is likely to rear, and this tendency has been exacerbated under farm conditions by genetic selection pressure for increased prolificacy. Piglet mortality from birth to weaning typically amounts to 16-20%, with the major causes attributed to stillbirth, crushing by dam and starvation. However, these ultimate causes mask the true predisposing factors, with interactive risk factors arising from the biology of the sow and piglets and the challenges of the neonatal environment. Intra-uterine competition for nutrients can result in a stillborn piglet or a live-born piglet with reduced viability, low birth weight and compromised chances for postnatal survival. Prenatal insults can impact on vigour and thermoregulatory abilities, resulting in a piglet unable to survive the challenges of asphyxia during birth, hypothermia following delivery and intense competition for colostrum. Reduction in piglet mortality requires co-ordinated genetic, nutritional, management and stockperson interventions. The incorporation of survival traits in genetic selection goals, the optimisation of maternal nutrition during breeding and gestation and the avoidance of prenatal maternal stress through appropriate environmental conditions will promote delivery of more vital piglets and stimulate good maternal behaviour. Supervision and assistance during farrowing, with stockperson intervention to facilitate early and adequate ingestion of colostrum by all piglets, provision of appropriate thermal microclimates to reduce hypothermia and skilful cross-fostering to ensure early establishment of litters of appropriate size and uniformity, are all key components of success. With an increasing societal focus on the ethical and welfare issues in pig production, but no alleviation of the financial pressures on pig farmers to remain competitive, the requirement to achieve a high number of piglets weaned per sow per year in an environment allowing adequate expression of sow behavioural needs will continue to pose challenges.

African Swine Fever (ASF)

African Swine Fever (ASF) is widely regarded as one of the most serious and damaging diseases affecting pigs worldwide. ASF was first recognised in Kenya in the 1920’s and is enzootic across a wide range of sub-Saharan Africa being maintained by infection of wild swine often asymptomatically and by infection of the soft tick Ornithodorus mubata. Until 1957, the disease had not been described outside Africa but then appeared in the Iberian Peninsula (Spain, Portugal, Andorra, Gibraltar, and a small part of France) and Sardinia, Italy where it was maintained in wild and feral pig populations and in Ornithodorus ticks. The disease is reported to spread at a rate of approximately 100km/year but jumped large distances due to transport of and exposure to infected meat products including allegedly by military movements. Several outbreaks have occurred in many European countries. The disease was diagnosed in the north of China in 2018 for the first time but has since spread rapidly throughout the country, believed to be the result of pig feed contamination followed by local spread. The disease is now entrenched in large areas of South-East Asia and is starting to have a huge impact on global pig meat supplies. In India, after the first ASF outbreaks occurred in Assam in January 2020, cases were also reported from other north-eastern states of Manipur, Meghalaya, Mizoram, Nagaland, Arunachal Pradesh and Sikkim. Following this, the disease spread to Bihar, Kerala, Punjab, Haryana, Gujarat, Jharkhand, Karnataka, Madhya Pradesh, Rajasthan, Tripura, Uttarakhand, Uttar Pradesh and Delhi has been reported. 

 ASF is caused by a virus of the group Arborvirus and is the only member of the Asfarvirida. It is a large DNA virus of which at least 22 distinct genotypes and pathogenesis varies between these genotypes. The virus is completely different and separate to the Pestivirus which causes Classical Swine Fever (CSF). However, the clinical and pathological signs of CSF are indistinguishable from ASF. The virus strain seen throughout eastern Europe since 2007 is highly pathogenic and over time can cause 100% mortality. Many pigs are simply found dead. In herds early cases may be noticed in which clinical signs range from high fever and depression, cyanosis (blue discolouration of the skin due to insufficient oxygen circulation), incoordination, respiratory disease, vomiting and diarrhoea including haemorrhagic signs, mucopurulent or haemorrhagic occulo-nasal discharge and reproductive effects including abortion. Death will typically follow within 7-10 days or often sooner. All age groups of pigs can be affected as the disease steadily moves around the farm population. At post mortem examination the carcass may reveal extensive haemorrhages which may include haemo-pericardium, haemo-peritoneum as well as frank haemorrhage in kidneys, spleen, lymph nodes as well as in the lumen of the gut and urinary bladder. Oedema may occur within the wall of the gall bladder and in the lungs.

ASF should be suspected if the following circumstances are encountered: (A). Rapid death or high fever in high-risk animals such as those at risk of exposure to kitchen food scraps, (B). High fever in a range of different age groups of pigs particularly if clinical disease as listed above is seen and (C). Haemorrhagic carcass seen at post mortem examination particularly if the epidemiological picture is suggestive of a primary infectious disease. If the disease is not ruled out clinically, restrictions should be imposed on the premises and laboratory testing (a combination of virus isolation, PCR and serology tests) is done to confirm or refute the diagnosis. Following confirmation of ASF on farm mass destruction of the whole population is to be undertaken and extensive and thorough cleaning of the premises is required. No vaccine has yet been successfully produced and used anywhere and control is based on early recognition, slaughter and cleaning and disinfecting of premises.

Classical Swine Fever (CSF)

Classical swine fever (CSF) is a highly infectious and often fatal viral disease of swine. It is caused by an enveloped RNA virus of the genus Pestivirus of the family Flaviviridae. CSFV is antigenically related to other Pestiviruses, mainly to the bovine viral diarrhoea virus (BVDV) of cattle and to the border disease virus (BDV) of sheep. CSFV naturally infects members of the Suidae family, i.e., domestic and wild pigs. CSF is one of the most important diseases of pigs causing high mortality with annual loss of approx. Rs 4.299 billion. CSFV has only one serotype, but has minor antigenic variability between strains. The virus is moderately fragile and does not persist in the environment or spread long distances by the airborne route. Classical swine fever virus is distributed worldwide. It is considered endemic in certain countries of Central and South America, in the Caribbean basin, and many pork-producing countries in Asia. The first documented report on CSF in India dates back to 1962. A total of 611 outbreaks of CSF in India were reported during 2000-2015. The disease is enzootic in most of the pig producing states and particularly in the North-Eastern states of India. Outbreaks of CSF have not only been reported from different states of India, but the occurrence of CSF virus in the tissues of pigs slaughtered for human consumption has also been reported.  The pig is the primary source of CSFV infection, either via infected live animals or uncooked pork products.

Classical swine fever is characterized by fever, haemorrhages, ataxia and purple skin discoloration. The clinical presentation varies depending on host characteristics and the particular virus strain causing the infection. The principal lesion produced by CSFV infection is a generalized vasculitis, clinically manifested as haemorrhages and cyanosis of the skin, notably at the ears, lower abdomen and extremities. There may also be a generalized erythema of the skin. Vasculitis in the CNS leads to incoordination (staggering gait) or even convulsions. Histologically, nonsuppurative encephalitis with a characteristic vascular cuffing is commonly observed. CSF occurs in several forms, including acute, chronic and subclinical. Whole blood collected with EDTA as an anticoagulant can be used for virus isolation or virus detection, particularly during the viraemic phase of the infection. The serum samples   are taken when serological tests for detecting CSFV antibodies are pursued. Nasal swabs and tonsil scrapings are commonly collected clinical samples that detect the virus (i.e., viral RNA). The oronasal route sheds substantial amounts of CSFV from infected animals into the environment, particularly early during infection. The CSFV diagnosis has been confirmed by RT-PCR and nucleotide sequence data showed the presence of 1.1 and 2.2 subgroups.

Commercial CSF live, attenuated vaccines (LAVs) are safe and highly efficient, inducing protection within the first week after vaccination. These LAVs, originally C strain, have been used worldwide for over 50 years with an extraordinary safety record. In India, the lapinized swine fever vaccine has been used in the country to protect pigs against the disease, but the vaccine is not sufficient and is facing constraints in its production. Classical swine fever is a reportable disease. No treatment is available. In countries where the virus is endemic, prophylactic vaccination is used. Control is usually tightly regulated by local laws that establish strict sanitary measures. If systematically applied, vaccination may lead to the elimination of CSFV from swine herds. A lapinized CSF vaccine (Weybridge strain, UK) is being used in India since 1964 for controlling the disease. A Live attenuated Classical Swine Fever (CSF) cell culture vaccine (Indigenous strain) was released by ICAR-IVRI in 2020. The cell culture attenuated CSF virus vaccine will be the only alternative to protect pigs against the disease. Besides the vaccine, early diagnosis and understanding on the epidemiology of the disease are important not only to prevent the spread of the disease but also to evolve suitable strategy to control the disease in India.

Porcine Reproductive and Respiratory Syndrome (PRRS)

Porcine Reproductive and Respiratory Syndrome (PRRS) is an acronym (Porcine Reproductive and Respiratory Syndrome) for a relatively new viral disease of pigs that is characterized by two overlapping clinical presentations- reproductive impairment or failure in breeding animals and respiratory disease in pigs of any age. PRRS was first reported in the USA in 1987. Since then, outbreaks of PRRS and successful isolation of the virus have been confirmed throughout North America, Asia, South America, Africa and Europe. Confirmed cases of PRRS was first reported in 2013 in Mizoram, India. Subsequently, it was sero-positively diagnosed from Mizoram, Meghalaya, Assam, Nagaland and Manipur states. Outside North-Eastern region, high sero-posivity was reported in pig samples from Punjab. The causative agent of PRRS is the PRRS virus, which is an RNA virus classified under the order Nidovirales, family Arteriviridae and genus Arterivirus. There are two related but antigenically and genetically distinguishable strains: Genotype 1, with the prototype Lelystad virus representing the viruses predominating in Europe and Genotype 2, represented by VR 2332, the prototype of strains originally mostly found in North America. After infection of a naive herd, exposure of all members of the breeding population is inconsistent, leading to development of naive, exposed and persistently infected subpopulations of sows. Aerosol transmission of the virus has been confirmed. Experimental transmission via certain species of insects (mosquitoes [Aedes vexans] and house flies [Musca domestica]) has been reported. Porcine reproductive and respiratory syndrome appears to have two distinct clinical phases: reproductive failure and post-weaning respiratory diseases.

The reproductive phase of the disease includes increases in the number of stillborn piglets, mummified foetuses, premature farrowing’s and weak-born pigs. Stillbirths and mummies may increase up to 25-35% and abortions can be >10%. Anorexia and agalactia are evident in lactating sows and result in increased (30%–50%) pre-weaning mortality. Suckling piglets develop a characteristic thumping respiratory pattern. Histopathologic examination of lung tissue reveals a severe, necrotizing interstitial pneumonia. PRRS is capable of crossing the placenta in the third and possibly second trimester of gestation. Piglets may also be born viraemic and transmit the virus for 112 days after infection. Performance after weaning is also affected. Outbreaks of the reproductive form of PRRS have been reported to last 1-4 months, depending on the facilities and initial health status of the pigs. In contrast, the post-weaning pneumonic phase can become chronic, reducing daily gain by 85% and increasing mortality to 10-25%. Numerous other pathogens are commonly isolated along with PRRS virus from affected nursery or finishing pigs. The bacteria such as Streptococcus suis, Escherichia coli, Salmonella Choleraesuis, Haemophilus parasuis and Mycoplasma hyopneumoniae have been reported, as well as viruses such as porcine respiratory coronavirus and swine influenza virus.

Diagnosis of PRRS is done by serology or PCR. The most commonly used serologic assay to help diagnose Porcine Reproductive and Respiratory Syndrome is the ELISA. It measures IgG antibodies to PRRS virus. Tests for PRRS virus include PCR, virus isolation, and immunohistochemistry. Nucleic acid sequencing of the open reading frame 5 region of the virus is an excellent tool for epidemiologic investigations in the field to confirm similarity between isolates recovered from different sites. There are no effective treatment of PRRS, although modified-live vaccines provide partial protection against infection. A comprehensive program of biosecurity, targeting both mechanical and airborne risk factors, is essential to maintain a naive herd status.

Foot and Mouth Disease (FMD)

Foot and Mouth Disease (FMD) is a highly contagious viral infection of domestic and wild cloven-hooved animals including pigs. Cattle, sheep, pigs, goats, camelids, deer, buffaloes, elephants are susceptible host. It is found in the Middle East, Africa, Asia and South America. Foot and Mouth Disease virus is a picornavirus. There are 7 distinct serotypes of FMD virus: O, A, C, SAT 1, SAT 2, SAT 3 and Asia 1. FMD is one of the most contagious animal disease and infected animals excrete the virus in fluid from ruptured blisters, exhaled air, saliva, milk, semen, faeces and urine. Virus transmission can begin before blisters appear. The primary method of transmission within herds and flocks is by direct contact or via respiratory particles and droplets. Pigs are potent excreters of airborne viruses. Spread of infection between properties and areas is frequently due to movement of infected animals or contaminated vehicles, equipment, people and products. Windborne spread of infected aerosols can occur under the right conditions. Typical clinical signs of FMD in pigs include: pyrexia, though this clinical sign is inconsistent. Severe foot lesions and lameness, with detachment of the claw horn, especially when housed on concrete occurs. Vesicles on pressure points of limbs, especially along the carpus, resulting in knuckling is seen. Vesicular lesions on the snout and abortion are not uncommon. Mouth lesions are washed with 1% potassium permanganate solution and Boro-glycerine (Boric acid glycerine paste). Foot lesions may be washed with 1% potassium permanganate solution or 0.5-1% baking soda (sodium bicarbonate) and to be applied with antiseptic cream. The Government’s response to FMD is to quickly eradicate the disease through a combination of strategies including: quarantine, animal movement controls, disposal of infected animals and decontamination of infected premises. Each FMDV strain requires a specific vaccine to provide immunity to a vaccinated animal. Its prevention is based on the presence of early detection and warning systems and the implementation of effective surveillance among other measures. A bi-annual vaccination based FMD Control Programme (FMDCP) was launched by the Government of India in 2004.

Pseudorabies

Pseudorabies, Aujeszky’s disease or mad itch. is a disease of swine that can also affect several species of farm and pet animals. In India, the status of the disease is not clear except for 2 isolated reports in early 1970’s.  Pseudorabies virus (PRV) is a contagious herpesvirus that causes reproductive ailments viz., abortion, stillbirths, respiratory problems and occasional deaths in breeding and finishing hogs. Infected newborn pigs may exhibit nervous system clinical signs. PRV is primarily spread through direct animal-to-animal (nose-to-nose) contact between an infected, shedding pig and a non-infected pig. It may also be spread by sexual contact. If present on inanimate objects, such as boots, clothing, feed, trucks and equipment, the virus can also spread from herd to herd and farm to farm. Clinical signs in pigs depend on the age of the affected animal. In piglets, central nervous systems signs, incoordination, sneezing, coughing and high mortality are seen. In adult pigs coughing, fever, pneumonia, central nervous systems signs and reproductive signs such as failure to breed, abortions, mummified piglets, stillbirths and small litters are reported. Adult pigs often have low mortality and the virus can remain hidden in the pig in a carrier state for long periods of time. There is no treatment but antibiotic medications can control secondary bacterial infections. PRV vaccines are available in foreign countries particularly in USA. Pseudorabies can be prevented primarily through biosecurity and sound management practices that include disease control and prevention.

Swine Flu

Swine flu is a respiratory disease of pigs caused by an influenza virus. The first flu virus isolated from pigs was influenza A H1N1 in 1930. This virus is a subtype of influenza that is named for the composition of the proteins hemagglutinin (H) and neuraminidase (N) that form its viral coat. Since the 1930s, three other subtypes of flu viruses also have been isolated from pigs, including H1N2, H3N1, and H3N2. The emergence of H3N2 in pigs occurred in the late 1990s and is suspected of having been transmitted to pigs from humans. Although swine influenza viruses are similar to the influenza viruses that circulate among humans, swine viruses possess distinct antigens. About 25- 30% of pigs worldwide carry antibodies to swine influenza viruses, which indicates that these animals have been exposed to swine flu. The disease is endemic in pigs in the United States and in some regions of that country more than 50% of pigs carry antibodies to swine influenza viruses. Infection with any of these viruses causes a flu-like illness in pigs, which typically occurs in the fall and early winter. Symptoms of infection include coughing (barking), fever and nasal discharge and illness generally lasts about a week. The virus is spread rapidly among pigs and is easily spread to birds and humans who come into contact with the pigs or contaminated food or bedding or who inhale infectious particles in the air. Humans infected with swine influenza virus may experience fever and mild respiratory symptoms, such as coughing, runny nose and congestion. Some persons experience diarrhoea, chills and vomiting. Swine influenza virus rarely causes death in humans. There are no specific drugs available for treatment of swine flu in pigs and treatment is thus supportive. Providing a clean and dry environment and keeping infected pigs separate from healthy pigs are essential approaches to controlling the disease. In many cases, antibiotics are administered to prevent the emergence of bacterial infection. Outbreaks of swine flu in pigs can be prevented through vaccination against the viruses. The spread of the virus among pigs also can be controlled through sanitary practices, such as disinfecting areas that were occupied by infected pigs, disposing of contaminated bedding and washing hands after handling infected animals.

Mycoplasmal Pneumonia in Pigs (Enzootic Pneumonia)

Mycoplasmal pneumonia is a chronic, typically clinically mild, infectious pneumonia of pigs. Disease is caused by Mycoplasma hyopneumoniae, which is a common cause of pneumonia in pigs worldwide. Clinically, disease is characterized by a persistent dry cough, impaired growth, occasional flares of overt respiratory distress and a high incidence of lung lesions in slaughtered pigs. It tends to become endemic in infected herds. The outbreaks of Mycoplasmal pneumonia may impair growth rate and feed conversion. In swine units with good disease control measures, Mycoplasmal pneumonia may remain largely subclinical. Mycoplasma hyopneumoniae causes pneumonia in pigs which is sometimes referred to as enzootic pneumonia. M. hyopneumoniae is a host-specific pleomorphic organism that lacks a cell wall, is fastidious and smaller than most bacteria. It can be cultured in specially prepared media, but isolation from field cases is difficult. It is rapidly inactivated in the environment by disinfectants but it may survive longer in cold weather and depending on the surface of the material. Mycoplasmal pneumonia is also frequently complicated by other mycoplasmas, bacteria and viruses, which affect the severity of the disease. It is recognized as part of the porcine respiratory disease complex. In most countries that use modern pig-farming methods, the lungs of 30-80% of pigs slaughtered show lung lesions associated with M. hyopneumoniae infection. Pigs of all ages are susceptible. Transmission to suckling piglets can occur from sows of all parities but is most prevalent in first-parity (gilt) litters.

Prevalence of M. hyopneumoniae at weaning age has been suggested as an indicator of disease in finishing pigs. The onset of the disease may be most evident in the finishing stage at ~18-20 weeks of age. The incidence of lung lesions is highest in pigs 3-5 months old. Immunity develops slowly, followed by regression of the lung lesions. Older growing and mature pigs may recover from the disease completely, although persistence of the mycoplasma in the respiratory tract of infected animals has been confirmed for up to 7 months. Non-productive coughing is the most common sign of Mycoplasmal pneumonia and is most obvious when pigs are roused. In endemically infected herds, morbidity is high, but clinical signs may be minimal, and mortality is low. Average daily weight gain and days to market weight are common production parameters negatively affected. On post mortem examination, areas of affected lungs are gray or purple, most commonly in the apical and cardiac lobes and consolidated. Old lesions become clearly demarcated and eventually heal, leaving visible scars. The associated lymph nodes may be enlarged. Histologically, inflammatory cells are present in the bronchioles and there is perivascular and peribronchiolar cuffing and extensive lymphoid hyperplasia.

 Disease is diagnosed by typical clinical, histopathologic and herd epidemiologic findings which are usually suggestive of Mycoplasmal pneumonia. M. hyopneumoniae can be demonstrated in impression smears of the cut surface of affected lung, identified by fluorescent antibody technique or by in situ hybridization and isolation and identification of Mycoplasma in culture. Recently, PCR tests have become the most commonly used tool for detection of  in various samples types. Partial disease control can be achieved with improved management, vaccination and medication. The economic effects of Mycoplasmal pneumonia in pigs can be reduced by improvements in housing and husbandry, particularly ventilation and space allowance. “All-in/all-out” management of pigs from birth to market is extremely effective at reducing negative effects of disease. Following this practice improvement in growth performance and reduction in lung lesions are achieved. Commercial inactivated Mycoplasmal bacterins consist of adjuvanted whole-cell preparations. Bacterins induce protection against development of gross lesions and significantly reduce clinical signs (coughing) in growing pigs. However, vaccination does not prevent infection.

Intestinal Salmonellosis

Enteropathogenic salmonellae cause inflammation and necrosis of the small and large intestines, resulting in diarrhoea. Infection with certain serotypes may be accompanied by generalized sepsis. Pigs of all ages are susceptible; however, intestinal salmonellosis is most common in weaned and growing-finishing pigs. Salmonella enterica serotype Choleraesuis, variety Kunzendorf (S. Choleraesuis), is one of the most common Salmonella species affecting pigs. It sometimes produces necrotizing enterocolitis; more commonly, it is associated with septicaemic disease characterized by hepatitis and pneumonia. Intestinal Salmonellosis in pigs has traditionally been associated with either, S. Choleraesuis or S. Typhimurium. Recently, S. Enterica serotype 4,[5],12:i:-has been detected with increasing frequency in pigs with clinical signs of disease and it has become one of the predominant serotypes isolated from diseased swine. S. Typhisuis infection is less common and is associated with chronic ulcerative colitis. Sources of infection with these serotypes are primarily asymptomatic carrier pigs; however, rodents and contaminated feed and premises may also be sources. Intestinal salmonellosis is most often observed in pigs from weaning up to about 5 months old but it can occur at other ages. Affected pigs are commonly febrile, with reduced feed intake and have liquid yellow faeces that may contain shreds of necrotic debris. Diarrhoea in individual pigs usually lasts 3-7 days and it may recur for multiple bouts.

Pigs infected with enteropathogenic salmonellae (S. Choleraesuis, S. Typhimurium, and S. 4,[5],12:i:-) have an inflamed, segmentally thickened distal small intestine and colon, usually with necrotic debris on the mucosal surface. Mesenteric lymph nodes are variably enlarged, oedematous and reddened. Mucosal ulceration may or may not be evident and a small amount of haemorrhage may be observed in acute cases. Rectal strictures occasionally occur as a sequela. S. Typhisuis infection produces distinctive lesions that include multifocal, chronic, deep mucosal ulcers with central cores of caseo-necrotic debris (“button” ulcers). Condition is diagnoses by culture and serotyping and histologic examination. PCR assays are increasingly available, often with serotype-level specificity, that can reduce the time to final etiologic diagnosis. Histologic examination of affected intestine and liver tissue to differentiate intestinal salmonellosis from proliferative enteropathy and swine dysentery is of high diagnostic value. Treatment and control of disease includes antimicrobial treatment based on results of minimum inhibitory concentration testing and vaccination. Live avirulent vaccines administered either intranasally or via drinking water are effective for prevention of disease caused by S. Choleraesuis and S. Typhimurium. Avirulent vaccines may also effectively reduce levels of salmonellae in the tissues of swine at slaughter.

Brucellosis

Swine brucellosis is an infectious disease of swine caused by Brucella suis (B. suis) biovars 1 or 3. Swine exposed to B. suis develop a bacteraemia. Infection can then localize in various tissues. It is usually spread mainly by ingestion of infected tissues (i.e. aborted foetuses and other tissues of infected animals) or fluids (i.e. urine, semen etc.). Infected boars may transmit the disease during mating. The disease typically causes chronic inflammatory lesions in the reproductive organs which can cause abortions, infertility and low milk production. It may also localize in joints, leading to lameness. Common manifestations are abortion, temporary or permanent sterility, orchitis, lameness, posterior paralysis, stillborn, mummified or weak piglets. Treatment in affected animals is not curative. Disease prevention is the best approach since there is no vaccine or treatment for swine brucellosis. It is important to note that swine brucellosis is potentially a zoonotic disease. People in direct contact with potentially infected swine should take precautions as directed by public health experts.

CONCLUSIONS

The pig population in India is 9.06 million but it experienced an over 12.0% decrease. Pigs make up just 1.7% of the total livestock population in India but pork is one of important animal protein source in the country for down trodden communities and people of North-East and certain other regions of country. Pig farming is an integral part of the livelihood for the specific rural community. As the demand for pork and its products in India grows, the socio-economic impact of pig diseases has become more significant than ever before. African Swine Fever, Classical Swine Fever, Porcine Reproductive and Respiratory Syndrome, Swine Flu and Foot and Mouth Disease are the major economically important  emerging and remerging diseases in pigs in India and are causing serious economic losses in their swine industry. Mycoplasmal Pneumonia, enteric salmonellosis, brucellosis and piglet mortality are other causes of concern to pig farmers. The initiatives put in place by the Government of India mostly target strengthening swine disease control as well as promoting good swine health management practices. More research projects on swine health are required. A control strategy and action plan for swine diseases should be developed at national, state and regional levels based on inputs of FAO and OIE. Contingency and early detection surveillance plans for swine diseases based on OIE international standards and FAO Manual may be developed.