Lungworms (Metastrongylus spp.) demonstrated in domestic pigs with respiratory disease: was there a clinical relevance?

Abstract

Background An outdoor pig herd was affected by severe respiratory disease in one out of three pastures. At necropsy, Mycoplasma hyopneumoniae and Pasteurella multocida were detected in the lungs, as well as the lung worm Metastrongylus apri. The life cycle of Metastrongylus spp. includes earthworms as intermediate hosts, and since domestic pigs mainly are reared indoors, lungworm infections have not been diagnosed in domestic pigs in Sweden for decades, not even in pigs reared outdoors. Therefore, this disease outbreak was scrutinised from the view of validating the impact of Metastrongylus spp. Results At the time of the disease outbreak, neither eggs of Metastrongylus spp., Trichuris suis nor Ascaris suum were detected in faeces of pigs aged ten weeks. In contrast, five-months-old pigs at the pasture with respiratory disease shed up to 3800 eggs per gram (Epg) of Ascaris suum and up to 1100 Epg of Trichuris suis, whereas eggs of these parasites were not demonstrated in healthy pigs aged six months at another pasture. Low numbers of eggs from Metastrongylus spp. (< 150 Epg) were seen in faecal samples from both these age categories. At slaughter, seven weeks later, ten normal weighted pigs in the preceding healthy batch were compared with ten normal weighted and five small pigs from the affected batch. Healing Mycoplasma-like pneumonic lesions were seen in all groups. All small pigs shed eggs of Ascaris suum in the faeces, compared to around 50% of the larger pigs. Metastrongylus spp. were demonstrated in 13 of the 25 pigs (52%), representing all groups included. Conclusion As Metastrongylus spp. were demonstrated regardless of health status, and also in another healthy outdoor herd, the impact of Metastrongylus spp. on the outbreak of respiratory disease was depreciated. Instead, a possible association with a high burden of Ascaris suum was suggested to have preceded the severe outbreak with respiratory disease in the affected herd. Further, it was concluded that Metastrongylus spp. will escape detection at routine meat inspections made at slaughterhouses, and as they appeared to generally not induce clinical signs of respiratory disease Metastrongylus spp. may be more common in outdoor production than previously believed.

Granulomatous pneumonia due to metastrongylus species associated with <i>Mycoplasma hyopneumoniae</i> and <i>Pasteurella multocida</i> in slaughtered pigs

“…Actinobacillus pleuropneumoniae (Choi et al, 2003;Hansen et al, 2010;Fablet et al, 2012). Respiratory parasites and migratory stages of helminths have also been reported to have an impact on the PRDC (Wallgren & Pettersson, 2022). In this study, the mechanism leading to MYHO-lungworm interaction leading to co-infection is not known.…”

“…Although there were previous reports on the prevalence of metasrongylosis in Nigeria (Stockdale 1976;Nssien and Adesehinwa, 1999) and other countries (Sibila et al, 2010;Oba et al, 2021;Wallgren & Pettersson, 2022). Report of coinfection associated with Metastrongylus spp., M. hyopneumoniae and Pasteurella multocida is scanty in literature, only a few reports such as those of Wallgren & Pettersson (2022) in Sweden, Oba et al (2021) in Northern Uganda and Sibila et al (2010) in wild boars and had been documented. In Nigeria, despite high prevalence of pneumonia and metastrongylosis, co-infection associated with MHYO and Metastrongylus spp.…”

“…The adult lungworm has a predilection for the bronchi and bronchioles (Nssien & Adesehinwa, 1999, Taylor et al, 2016. Different stages of Ascaris suum have also been observed in the airway of pigs (Wallgren & Pettersson, 2022). Grossly, lungworm lesions were reported to be usually mild or even absent; however, presence of larval stages, adult worm and eggs may cause verminous or nodular inflammation of the airway and pneumonia (Marruchella et al, 2012) which may cause obstruction of the bronchi and bronchioles (Poglayen et al, 2016) resulting in bronchitis and bronchiolitis, respectively (Stockdale, 1976).…”

“…Grossly, lungworm lesions were reported to be usually mild or even absent; however, presence of larval stages, adult worm and eggs may cause verminous or nodular inflammation of the airway and pneumonia (Marruchella et al, 2012) which may cause obstruction of the bronchi and bronchioles (Poglayen et al, 2016) resulting in bronchitis and bronchiolitis, respectively (Stockdale, 1976). These can be compounded by management, environmental factors and nutritional deficiencies (Marruchella et al, 2012), as well as some pathogenic bacteria such as Pasteurella multocida (Wallgren & Pettersson, 2022). Although there were previous reports on the prevalence of metasrongylosis in Nigeria (Stockdale 1976;Nssien and Adesehinwa, 1999) and other countries (Sibila et al, 2010;Oba et al, 2021;Wallgren & Pettersson, 2022).…”

“…These can be compounded by management, environmental factors and nutritional deficiencies (Marruchella et al, 2012), as well as some pathogenic bacteria such as Pasteurella multocida (Wallgren & Pettersson, 2022). Although there were previous reports on the prevalence of metasrongylosis in Nigeria (Stockdale 1976;Nssien and Adesehinwa, 1999) and other countries (Sibila et al, 2010;Oba et al, 2021;Wallgren & Pettersson, 2022). Report of coinfection associated with Metastrongylus spp., M. hyopneumoniae and Pasteurella multocida is scanty in literature, only a few reports such as those of Wallgren & Pettersson (2022) in Sweden, Oba et al (2021) in Northern Uganda and Sibila et al (2010) in wild boars and had been documented.…”