Setaria marshalli infection in neonatal calves

The first genetic characterization of Setaria marshalli (Nematoda, Spirurida) with reliable DNA barcoding based on a mitochondrial genetic marker

Setaria marshalli is a mosquito-borne filarial nematode that causes infection in calves younger than two years old. In the present study, nematodes were obtained from a calf in Japan and morphologically identified as S. marshalli. Additionally, the partial cytochrome oxidase subunit I (COI) region (596 bp) was analyzed for the first time to establish a reliable DNA barcode. Nucleotide sequences of COI were identical among the seven worms obtained. The COI region can be a useful marker for species discrimination in the case of S. marshalli since nucleotide variations observed between the closest congener, Setaria cervi (51/596 bp), were sufficient to allow species discrimination. However, the phylogenetic relationship of S. marshalli with its congeners was unclear in a maximum likelihood tree. We found that the partial COI sequence of S. marshalli analyzed in the present study matched a relevant section of the complete mitochondrial genome of S. labiatopapillosa that was deposited in the International Nucleotide Sequence Database. This finding suggests that S. marshalli was misdiagnosed as S. labiatopapillosa in a previous study. It is crucial to conduct accurate morphological analyses to obtain reliable molecular information regarding Setaria nematodes.

Cerebrospinal Setariosis with Setaria marshalli and Setaria digitata infection in Cattle

Setaria digitata and S. marshalli larvae were observed in the cerebrospinal cavity of 2 paralyzed cattle in Taiwan. The 2 affected cattle showed quadriplegia and lumbar paralysis, respectively. At necropsy, which was performed 7 days after the 7-month-old cattle became quadriplegic, three and nineteen S. marshalli larvae as well as two female adult worms were found in the cranial cavity, spinal cavity and peritoneal cavity of the cattle, respectively. Necropsy on the other 8-month-old cattle was also performed 3 days after it showed lumbar paralysis, and ten S. digitata larvae were found in the spinal cavity. In both cattle, many mononuclear inflammatory cells mixed with a few eosinophils were seen accumulated in the connective tissue around the root of the spinal nerves. Infiltration of eosinophils and mononuclear inflammatory cells into the epidura and arachnoidea of the brain were also observed. The major inflammatory cell was lymphocytes, but neutrophils and eosinophils were also present. The number of cells in the cerebrospinal fluid collected initially from the two affected cattle were 105/0.01 ml and 143/ 0.01 ml, respectively. This is the first report of cerebrospinal setariosis in cattle associated with S. marshalli.

Ocular infection of cattle with Setaria digitata

One 5-month-old female native Korean calf and a 2-year-old female Holstein cow raised in two farms about 4 km apart from each other in Korea, were found to have the left eye opaque, which included motile white worms in the aqueous humor. The parasite removed from the left eye of the calf was identified as Setaria digitata based on both light and electron microscopic features. The ocular infection with S. digitata reported herein may document the first aberrant case in Korean cattle.