Sarcoptic mange infestation in pigs: an overview

Abstract

Sarcoptic mange infestation in pigs is caused by Sarcoptes scabiei var. suis. It is the most common mange infestation of pigs. The parasite is distributed worldwide. Pig owners are generally concerned about the internal parasitic infections and ignored the external parasitic infestations. But the external parasitic infestation with S.scabiei var. suis has economic significance as it causes morbidity, mortality, decreased fertility and feed conversion ratio in pigs. Keeping in view of importance of S. scabies var. suis infestation in pigs, this communication discussed about the present and past research works done on S. scabies var. suis infestation in pigs, particularly its prevalence, life cycle, pathological lesions, clinical symptoms, haematobiochemical changes, diagnosis, treatment and control, to have an idea about this infestation at a glance. It has been concluded that the research work done on sarcoptic mange infestation in pigs in India is less in comparison to other countries. It may be due to its consideration as a neglected parasite or due to it’s under report. Organization of awareness programs for the farmers by extension personalities or other authorities might be able to save the farmers from economic losses due to this infestation.

Introduction

The population of pig in India is 11.13 million as per Livestock Census (2007) with highest population in Assam followed by Uttar Pradesh, West Bengal, Jharkhand and so on. Generally pigs are reared by the tribal population of our country for their livelihood. This population of pigs has been found to be infected with internal parasites or infested with external parasites. There is lack of awareness amongst farmers about infection or infestation of parasite on their pigs and whatever little bit awareness is there, it remains within themselves that are related to internal parasitic infections only. For this, pig owners are generally concerned about the internal parasitic infections and ignored the external parasitic infestations. But external parasitic infestations particularly mange mite infestation in pigs are very much important because of its economic significance (Damriyasa et al. 2004). Sarcoptic mange infestation in pigs are caused by the mite Sarcoptes scabies var. suis which causes significant morbidity and mortality in wild, domestic and farm animals (Walton and Currie 2007; Dagleish et al. 2007; Eo et al. 2008; Chhabra and Pathak 2011). S. scabies var. suis is the most common cause of mange infestation in swine. In addition to morbidity and mortality, another important aspect of this infestation is that it may cause damage to pig handlers which cause severe itching as it has been reported that 65.2 % pig handlers out of 46 studied had symptoms of S. scabiei and diagnosis of S. scabiei mite in 20 persons have been done (Chakrabarti 1990). Besides, improved there are reports of mange control programme to reduce pig mortality (Forgues et al. 1988). Keeping in view of importance of S. scabies var. suis infestation in pigs, the present communication have been made to have an overall idea regarding present and past research works done on S. scabies var. suis infestation at a glance (Fig. 1, 2).

Fig. 1.

Dorsal view of Sarcoptes scabies var. suis under of microscope

Fig. 2.

Loss of hair from the thickened skin of mite infested pig

About the parasite

Sarcoptes scabies var. suis are small tiny parasite of the Family Sarcoptidae and the Order Acarina. In length, these mites are up to 0.5 mm long and from dorsal aspect, only two pairs of anterior legs can be seen. They can be observed only under microscope.

Life cycle

Eggs are laid by the female parasites in the skin tunnels at the rate of 1–3 eggs per day. After a period of 5 days, the eggs hatched to form larvae. Larvae moult to form nymph and further moulting of nymph form adult. It takes about 10–15 days to complete the life cycle of this parasite. The adult female parasite can live up to 30 days. These parasites have no capacity to reproduce outside the host, but the mite may survive outside the pig for up to 12 days at a temperature of 7 °C to 18 °C and a relative humidity of 65 to 75 % (Jacobson et al. 1999).

Prevalence

The parasite was first reported in 1857 and now it is distributed worldwide (http://www.uaex.edu/Other_Areas/publications/PDF/FSA-3077.pdf). The reports of occurrence of S. scabiei var. suis infestation in pigs from abroad and India are available (Chellapandian et al. 2004; Rueda-Lopez 2006; Loewenstein et al. 2006a). Gill et al. (1990) studied a total of 583 pigs of Indian Punjab and typical sarcoptic lesions were observed in 80.6 % pigs and 42.76 % pigs showed the presence of Sarcoptic scabiei. A perusal of available literature revealed that recently in India most of research work on sarcoptic mange infestation in pigs has been undertaken in the state Jharkhand (Prasad et al. 2001; Minz 2002; Sinha et al. 2004; Kumar et al. 2005, 2007; Minz et al. 2006). Apart from Jharkhand, reports of this infestations are available from Tripura (Roy 2000), North India (Dwivedi and Sharma 1985, 1986; Chhabra and Jakhar 1994; Mukherjee 1996) and other parts of the country (Subramanian et al. 2001; Maiti et al. 2004; Rajeshwari et al. 2004). Among suspected skin lesions of pigs from Chattishgarh, Maiti et al. (2004) found 37.50 % pigs were affected with sarcoptic mange. In North-Eastern region of India, where population of pigs are more and they are maintained in the village in unorganized way as well as in organized farms, reports of S. scabiei var. suis infestation in pigs are available from that part of the country. Report of S. scabiei var. suis infestation in pigs maintained in a remote village of Ri-Bhoi District of Meghalaya are available (Anonymus 2009). In one organized farm of Meghalaya, presence of S. scabiei var. suis infestation were detected in five pigs out of 15 suspected pigs which were suffered from skin lesions (Das et al. 2010). In another study of Meghalaya, among suspected skin lesions of pigs maintained in both organized and unorganized way, overall 11.11 % pigs were found positive for S. scabiei var. suis infestation (Anonymus 2010). In a recent study, Rajkhowa et al. (2012) from Assam reported over all 23.61 % pigs is infested with S. scabiei var. suis in an organized pig farm of Assam. The infestation is restricted not only in sporadic forms but it may occur as an outbreak form also. Subramanian et al. (2001) reported about an outbreak of scabies in a piggery unit. The infestation has been found to be occur more in winter season than rainy season (Galhotra et al. 1980) with younger animals suffered more (44.53 %) than adult animals (24.37 %) (Rajkhowa et al. 2012).

In a recent study from Mbeya Region, Tanzania 2 % pigs have been found to be infected with S. scabiei var. suis (Braae et al. 2013). From Ghana 38.2 % pigs have been reported as infested with Saroptes suis (Permin et al. 1999). The prevalence of the infestation from Germany has been recorded as 45.4 % (Damriyasa et al. 2004). Alonso de Vega et al. (1998) reported 37 % of the 1,318 slaughtered pigs of southeastern Spain examined were found positive for S. scabiei var. suis infestations. The ear scrapings of 33.7 % pigs of northeastern Spain were diagnosed as positive for S. scabiei var suis infestations out of 818 pig samples examined (Gutierrez et al. 1996).

Pathological lesions and clinical symptoms

This parasite penetrate deep into the skin, produce itching sensation, cause stress and resulted loss of body weight of the infested pigs. Some times secondary bacterial infection may develop in the damaged skin caused by rubbing and scratching due to this mite infestation. In experimentally infested pigs, S. scabiei var. suis infestations causes excoriations on the luminal surface of the ear after seven days of initial infestations, developed encrusted lesions in the ears between third and eight weeks of infections, generalized pruritis accompanied by focal erythematous skin lesions with eosiniphilia and allergic reactions (Cargill and Dobson 1979a). In natural infestations in crossbred pigs (Hampshire X Khasi local) lesions were mostly observed in ears, head, neck region, shoulders, leg and back region of those pigs. The lesions were characterized by reddening of the infested area, formation of crusts, hyperkeratosis, and fall of hairs from the area with wrinkled, thickened, rough, raised and thick asbestos-like skin (Das et al. 2010). The main clinical symptoms observed in the naturally infested pigs were pruritis as a result affected pigs showed rubbing of the skin against the wall of the pen (Loewenstein et al. 2006b; Das et al. 2010). The infestation may be a hypersensitive form, characterized by pruritis and the presence of small red papules or a chronic form, characterized by crusts (Rambozzi et al. 2007). Naturally contact-infected S. scabiei var. suis pigs reported to have nine time higher pruritic behaviour in compare to non-infected pigs (Elbers et al. 2000).

Haematobiochemical changes

Pigs naturally infested with S. scabiei var. suis showed significant decreased value of haemoglobin (Hb), packed cell volume (PCV), total erythrocytic counts (TEC), serum copper, serum zinc and serum glucose with increased level of Alanine aminotransferase (Sinha et al. 2004). Reduced haematological values like Hb, PCV and TEC along with decreased level of biochemical constituents of serum such as Ca, P, Zn, Cu, total serum protein and albumin have been observed in naturally gastrointestinal nematode infected and sarcoptic mange infested desi pigs (Kumar et al. 2007).

Economic losses

There are several aspects of economic impact of S. scabiei var. suis infestation in pigs. It may be due to decreased growth rate, decreased fertility and lower feed conversion ratio due to the infestation. S. scabiei var. suis infestation have been found as detrimental for the production performance in pigs (Arends et al. 1990; Davies 1995; Elbers et al. 2000). In experimental S. scabiei var. suis infestations in growing pigs, a depressed mean growth rates from 9.2 to 12.5 % has been observed (Cargill and Dobson 1979b). The economic losses due to sarcoptic mange infestation are also caused by decreased fertility of sows and lower feed conversion ratio (Zimmermann and Kircher 1998). In a study, growth performance of piglets from S. scabiei var. suis infested and treated sows showed significantly higher (541.5 g per day) than piglets from S. scabiei var. suis infested and untreated sows (518.4 g per day), because naturally infested untreated sows transmit the infestation to piglets and thereby showed less growth performance (Mercier et al. 2002). The growth performance (average daily gain in gram per day) of naturally contact-infected S. scabiei var. suis pigs, in comparison to non-infected pigs has been found to be differ according to the period of infestations (Elbers et al. 2000). They recorded a decreased growth performance of 35, 50 and 41 g per day during 0–35, 35–112 and 0–112 days of infections, respectively.

Diagnosis

Diagnosis of S. scabiei var. suis infestation is not so easy because most of the infested animals showed subclinical infestation where skin lesions are usually not visible and specific lesions remained absent (Matthes et al. 1990). A direct method of examination of scrapings collected from the inside of the pina can be used for diagnosis (Gutierrez et al. 1996; Alonso de Vega et al. 1998) where collected materials are to be placed on a petridish and incubate at 30 °C for a minimum of 8 h and to be examined under low power of microscope. Examination of skin scrapings of suspected cases is the way of diagnosis of S. scabiei var. suis in field condition, although it’s specificity is 100 % but sensitivity is low (Kambarage 1991; Hollanders et al. 1995; Gutierrez et al. 1996). Digestion of suspected scraping materials with 10 % potassium hydroxide, then centrifugation followed by examination of sediment under microscope is the way of examination of skin scrapings of suspected cases (Soulsby 1986). One improved technique is digestion of scraping materials in 10 % potassium hydroxide and examination under microscope after sugar flotation for eggs, immature and adult parasites (Hollanders and Castryck 1988). This sugar flotation technique found to be more sensitive than direct method, as in a study sugar flotation technique detected 92.0 % infestation where direct method detected 33.5 % infestations (Gutierrez et al. 1996). In another study, Alonso de Vega et al. (1998) diagnosed 37 % pigs as positive using sugar flotation technique against 25.56 % by direct method. Whatever may be the method of examination of scraping materials, collection of scraping materials is very much important. Superficial scrapings are not recommended and during scraping oozing of blood are needed.

Serodiagnosis of infestation by detection of antibodies against S.scabiei var. suis infestation in pigs is another method of diagnosis. Earlier passive haemagglutination test was used for detection of serum antibodies of S. scabiei var. suis infested pigs using tanned bovine red blood cells and in experimentally infested animals titers ranged from 1:40 to 1:160 were detected (Wooten and Gaafar 1984). Now-a-days enzyme linked immunosorbent assays (ELISAs) are being used for detection of antibodies against S. scabiei var suis. The status of S. scabiei in pig herds is routinely monitored by serodiagnosis (Hejduk et al. 2011). Kessler et al. (2003) used indirect ELISA for detection of antibodies against S. scabiei var suis infested and treated pigs and opined that sensitivity of serological techniques must be taken into consideration for diagnosis particularly during its use in monitoring and eradication programs. For detection of antibodies in sera of S. scabiei infested pigs, Bornstein and Wallgren (1997) developed an ELISA where they observed the sensitivity and specificity of this serodiagnostic test is 87.8 and 99.5 %, respectively considering clinical diagnosis as gold standard. When skin scrapings were taken as gold standard, the test showed higher sensitivity (100 %) with lower specificity (32.8 %). Van der Heijden et al. (2000) validated an ELISA for detection of antibodies against S. scabiei in pigs. Antibody detection ELISA has been used successfully to monitor the eradication strategies against sarcoptic mange infestation in swine herds (Jacobson et al. 1999). Antigens prepared from extracts of S. scabiei var. vulpes have been used successfully in ELISA for detection of antibodies against S. scabiei infestation in pigs (Bornstein and Zakrisson 1993; Wallgren and Bornstein 1997). Now-a-days polymerase chain reactions are being used for diagnosis of various parasitic infections in different animals. Research regarding diagnosis of sarcoptic mite is going on and methods for collection to DNA extraction for such purposes has been beautifully mentioned by Alasaad et al. (2009). Sarcoptes-World Molecular Network (Sarcoptes-WMN) is working for immunodiagnosis and molecular diagnosis of sarcoptes using PCR (Alasaad et al. 2011).

Characterization of immunogenic proteins

There is a need to characterize the antigens used in antibody detection immunodiagnostic tests, to know about the immunogenic proteins of antigens involved in such immunodiagnosis. Sodium dodecyl sulfate–polyacrylamide gelelectrophoresis of antigens prepared from S. scabiei of pigs and its subsequent immunoblotting revealed seven immunodominant proteins (MW 36, 52, 66, 80, 110, 218 and >220 kDa) out of which five immunodominant proteins (MW 52, 66, 80, 110 and 218 kDa) also reacted with sera from S.scabiei negative pigs. Thus two immunodominant proteins of MW 36 and >220 kDa were identified as specific immunodominant proteins of S. scabiei of pigs (Rambozzi et al. 2007). They also reported that proteins of MW 36 kDa are more frequently recognized by hypersensitive pigs and proteins of MW >220 kDa is more frequently recognized by chronically infected pigs. Crude antigens prepared from S. scabiei var. canis or S. scabiei var. vulpes are generally used for ELISA. Characterization of such antigens after western blotting using sera from infected pigs revealed potential cross reactivity among S. scabiei (var. canis, suis and bovis) and hydrophobic S. scabiei antigens were detectable in the range of 40–50 kDa (Hejduk et al. 2011).

Treatment and control

This is the vital issue for farmer’s field as it has direct involvement with farmer’s economy. Treatment can be discussed in two aspects depending on the economical condition of the farmers. One can go for a treatment which is costly but less laborious like the use of injectable or oral preparations containing avermectin compounds or farmer’s can choice the medicines for local application, the use of which are laborious but comparatively less costly, like the use of some herbal preparations. Plants are being used for the treatment and control of acariasis in animals. A successful treatment was done by Dwivedi and Sharma (1985) using a mixture of onion, garlic, lemon, turmeric and powdered gunja (Abrus precatorius). Dwivedi and Sharma (1986) used locally a herbal preparation containing onion, lemon extract, garlic, turmeric powder and camphor in karanj oil once in a day for consecutive five days and infestation was eliminated within 5 days of application. Chhabra and Saxena (1998) described about phytotherapeutic agents for the control of acariasis in animals. The efficacy of extracts of six plant products i.e. mugwort, wormwood, garlic, tansy, hogwood and tea tree were evaluated against sarcoptic mange infestation in pigs (Magi et al. 2006). They found all plant products were toxic to swine mites and ethanol extracts of hogweed (Heracleum sosnowskyi Manden) showed highest efficacy which killed 57–93 % parasites in 2–4 weeks after two treatments with one week intervals. Application of a poly herbal cream containing oils of Linum usitatissimum, Eucalyptus globulus, Cinnamomum camphora, Ocium sanctum, Acorus calamus and powders of Tankana, twice daily for 7 days cured the infestation after 15 days of local application and after 20 days of treatment, skin became normal (Rajeshwari et al. 2004). Kumar et al. (2005) suggested the use of a herbal preparation consisting neem oil (50 ml), karanj oil (50 ml) and camphor (10 g) in control of S. scabiei infestation in pigs as they found application of this preparation cured 100 % infested pigs on 13 days post treatment. In another study, this group of researchers reported that use of these herbo-mineral preparations and ivermectin in the treatment of S. scabiei infestation in pigs could able to return the altered haemato-biochemical changes due to this infestation to almost its normal ranges during post treatment periods (Sinha et al. 2004). Kumar et al. (2007) successfully used cypermethrin and a mixture of herbomineral consisting neem oil (50 ml), karanj oil (50 ml), camphor (10 g) and sulphur (10 g) for the treatment of sarcoptic mite infestation in desi pigs. They also reported that the decreased haematological and biochemical parameters due to the infestation could be restored during post treatment periods. Three applications of 0.1 % amitraz at an interval of one week could able to control an outbreak in a piggery unit (Subramanian et al. 2001). Treatment and control of S. scabiei var. suis infestation was done successfully by treatment of pigs with 20 % phosmet @ 20 mg per kg. b.wt. and environment with 2 % trichlorphon (Kambarage 1991). Maiti et al. (2004) successfully used Cypermethrin in the treatment of sarcoptic mange in pigs. A brushing over thick scab may be needed before topical application of anti-sarcoptic agents to reach the agent up to the parasites.

Introduction of macrocyclic lactones (i.e. ivermectin, doramectin) for the treatment of S.scabiei var suis made it easy to treat the infestation. Lee et al. (1980) reported ivermectin @ 300–500 μg/kg body weight orally was 100 % effective against S. scabiei in pigs. Ivermectin @ 300 μg/kg body weight single or twice injected subcutaneously has been found effective to treat the infested pigs (Soll and Smith 1987; Gill et al. 1990). Injection of ivermectin subcutaneously @ 300 μg/kg body weight has been used successfully for the treatment of S. scabiei var. suis infestation in pigs (Seamen et al. 1993; Arends et al. 1999; Chellapandian et al. 2004). Treatment of S. scabiei var. suis with ivermectin @ 300 μg/kg body weight sub cutaneously at the start of fattening could able to change scratching behavior and dermatitis of treated pigs similar to mange free herds (Hollanders et al. 1995). Kumar et al. (2005) successfully used ivermectin @ 300 μg/kg body weight subcutaneously which cured the infested pigs on 7 days post treatment. Das et al. (2010) successfully used Ivermectin subcutaneously @ 200 μg/kg body weight in treatment of S. scabiei var. suis infestation in crossbred pigs. Ivermectin @ 300 μg/kg body weight was used for treatment of S. scabiei var. suis in pigs with a repeated treatment after two weeks and the medicine was found to have 90 % efficacy within two weeks. The symptoms of pruritis and scratching were disappeared from the day 21 post treatment (Rajkhowa et al. 2012). Naturally infested herd was successfully treated with a single intramuscular injection with doramectin (Jensen et al. 2002). In a comparative study of three medicines i.e., Doramectin (1 %) @ 300 μg/kg body weight single intramuscular injection, Diazonin liquid (20 %) 3 ml in one litre water dipping for 3 occasions at weekly intervals and deltamethrin 4 ml in one litre water dipping for 3 occasions at weekly intervals found 100 % efficacy of doramectin, 86.67 % efficacy of diazinon and 76.67 % efficacy of deltamethrin in treatment of natural S. scabiei infestation in pigs (Baishya et al. 2003). They recommended doramectin as drug of choice for the treatment of S. scabiei infestation in pigs as compared to other two medicines they used. Pathak and Chaurasia (2002) reported 100 % efficacy of doramectin for the treatment of S. scabiei infestation in pigs. The persistent efficacy of doramectin and ivermectin when evaluated by administration of these two medicines @ 300 μg/kg body weight in experimentally infected pigs it was observed that persistent efficacy of doramectin was double (18 days) in comparison to ivermectin (9 days) (Arends et al. 1999). Ohba et al. (1989) used different doses of ivermectin like 75, 150 and 300 μg/kg body weight with single subcutaneous injection against live mites and eggs of Sarcoptic sacbiei in pigs and found 300 μg/kg body weight was best for eradication of mites and eggs. One of the advantages of use of injectable avermectin compounds is that farmers can use the medicines as endectocidal agent’s means these medicines could be used for treatment of both internal parasitic infections and external parasitic infestations (Saeki et al. 1996; Yazwinski et al. 1997). Thus farmers can save their money in such type of simultaneous treatment. Treatments with systemic medicines may have the problems of drug residue in treated animals especially for food animals. To overcome this problem, experiments on development of antibodies to prevent infestations is going on. In this aspect, Sinha (2011) reported that immunization of piglets with whole mite extracts antigen (WMEAg) prepared from S. scabiei of pigs with FCA increased the value of lymphocytes, basophiles and eosinophils significantly on 30th and 60th. days of observations and developed immunity against S. scabiei in pigs.

Treatment of affected pigs along with monitoring of infestation is very much needed for the control of S. scabiei var. suis infestation in pigs. Repeated treatment is essential, as most of the acaridecide are not able to destroy the eggs. So, it is necessary to repeat the treatment after 14 days of first treatment, as per life cycle of the parasite. For eradication of infestation from the herd, (Spencer 2008) used ivermectin premix. He used ivermectin in feed and given a dose rate of 100 μg/kg body weight/day to pigs for a period of 7 days twice within 21 days, in a 7–7–7 program that means first 7 days medication followed by 7 days non-medication then 7 days medication. Along with this treatment, a strict bio-security could able to keep out the parasite from the herd. As the infection is contagious in nature, so segregation of infested pigs and treatment of the same is one of the ways of control strategy. Besides, overcrowding should be avoided to get rid of fresh infestation and cross infection. Pig should be purchased from a disease free herd and before entering it to the newly herd, they should be treated against sarcoptic mange. The parasite can survive out side the host. So, premises, cracks etc. of herd should be properly cleaned with acaricidal solution, to prevent reinfection of treated pigs. One of the main problem of control of S. scabiei var. suis is that, it can be transmitted from infected sows to suckling piglets. Treatment with Ivermectin (@ 300 μg/kg body weight single sub cutaneous injection) of pregnant sows just before they moved to farrowing unit could able to control the infestation both in pregnant sows without any health hazards and piglets (Mercier et al. 2002).

Conclusion

The research work related to sarcoptic mange infestation of pigs in India is less in comparison to some other countries. It may be due to the reason that sarcoptic mite is generally considered as a neglected parasite or the work is going on in a sporadic form which are not reflected due to under report. Besides, overall control of sarcoptic mange in pigs remains in awareness of farmers about this infestation and its economic importance. Organization of awareness programs for the farmers by extension personalities or other authorities could able to save the farmers from such economic losses.