A review of congenital tremor type A-II in piglets

Abstract

Congenital tremor (CT) is a neurological disease that affects new-born piglets. It was described in 1922 and six different forms, designated type AI-V and type B, are described based on the causative agents, as well as specific histological findings in the central nervous system (CNS). The various forms present with identical clinical signs consisting of mild to severe tremor of the head and body, sometimes complicated with ataxia. By definition, all A-forms have hypomyelination of the CNS, whereas there are no histopathological lesions with the B-form. The cause of the A-II form was long unknown, however, at present several different viruses have been proposed as the causative agent: porcine circovirus-II (PCV-II), astrovirus, PCV-like virus P1, and atypical porcine pestivirus (APPV). Currently, APPV is the only virus that has been proven to fulfill Mokili's Metagenomic Koch's Postulates. Following infection of the pregnant sow, the virus passes the placental barrier and infects the fetus. Interestingly, no clinical signs of disease have been associated with APPV in adult pigs. Furthermore, other viruses cannot be ruled out as additional potential causes of CT. Given the increased interest and research in CT type A-II, the aim of this review is to summarize current knowledge.

Genomic Rearrangement and Recombination of Porcine Circovirus Type 2 and Porcine Circovirus-Like Virus P1 in China

“…In general, there are no obvious changes observed in the central nervous system, peripheral nervous system, or skeletal muscle of the affected piglets through gross anatomical examination. However, different degrees of hypomyelination and mild vacuolization of the central nervous system are typical histological features ( 68 , 69 ).…”

Candidate genes for congenital malformations in pigs

“…Congenital tremor syndrome is specified as a rhythmic tremor of newborn piglets caused by the genetic background or environmental conditions during the intrauterine foetus development, leading to myelin deficiency, especially in the spinal cord, and approximately 50% morbidity (Mittsson, 2011). The syndrome appears in two types based on the presence of histopathological lesions in the central nervous system: type A with lesions and type B without lesions (Stenberg et al, 2020). Based on causality, type A can be further divided into five subtypes (A-I to A-V).…”

“…Previous studies have primarily focused on A-II to identify and understand the causative agents (Stenberg et al, 2020).…”

Pestivirus K (Atypical Porcine Pestivirus): Update on the Virus, Viral Infection, and the Association with Congenital Tremor in Newborn Piglets

“…CT is a neurological disorder that affects newborn piglets and is characterized by muscle spasms in the head and body, which can be localized or generalized [5,6]. The intensity of the tremors is variable, and in more severe cases, they include generalized tremors that result in difficulty in standing or walking and, consequently, inability to suckle, resulting in death due to starvation.…”

“…The intensity of the tremors is variable, and in more severe cases, they include generalized tremors that result in difficulty in standing or walking and, consequently, inability to suckle, resulting in death due to starvation. The clinical manifestation of CT is also called shaker pig syndrome, trembling pigs, or congenital myoclonus [6,7].…”