Gotch Ear in a Goat: A Case Report

Introduction

T he Gulf Coast tick (GCT), Amblyomma maculatum (Acari: Ixodidae), is a large, Nearctic and Neotropical, three-host tick (Hunter and Hooker 1907, Hooker et al. 1912) that parasitizes a wide range of vertebrate animals including goats in its various life stages (Ketchum et al. 2005). In cattle, adult GCTs generally prefer feeding on or in ears. A pathological condition in cattle ears, often called “gotch ear,” usually involving GCTs, has been previously documented (Gladney 1976, Williams et al. 1978, Edwards et al. 2010). The clinical definition of gotch ear was recently described as a condition of the ear in cattle associated with tick infestation, predominantly A. maculatum, exhibiting variable degrees of edema, and lesions at the tick-attachment sites on the outer or inner pinna(e) that included crusting, alopecia, erythema, and excoriation (Edwards et al. 2010). Curling of the tip of the pinna(e) and a loss of a portion of the ear(s) is sometimes also seen (Edwards et al. 2010). In that study, it was also determined that gotch ear resulted from the bite of GCTs and was not dependent on infection with R. parkeri (Edwards et al. 2010). Use of the term “gotch” when referring to this ear deformity may have originated from use of the word to refer to a pitcher or earthen jug, which may resemble the cupped shape of the deformed ear. To our knowledge, gotch ear has never been documented in a goat.

A yearling, castrated, male Saanen goat weighing 36.4 kg (80 lb) was evaluated on June 7, 2010 by the owner/veterinarian for drooping of the left ear of 1 day duration. Three partially engorged adult GCTs (two female and one male), A. maculatum, were removed from inside the left ear. No other tick species were observed on the animal. An 8-mm punch was used for biopsy of the tick attachment site on the affected ear. The sample was transferred to neutral-buffered 10% formalin and evaluated using hematoxylin and eosin stain and an immunohistochemical assay for spotted fever group Rickettsia spp. (Paddock et al. 1999). DNA extracts for each of the three attached ticks were evaluated using a nested polymerase chain reaction (PCR) assay designed to amplify a segment of the ompA gene based on a published protocol (Sumner et al. 2007). Extracts were also evaluated using a nested PCR assay designed to amplify a segment of the 17-kDa antigen gene as previously described (Paddock et al. 2004).

The wether's ear was treated topically at the tick attachment and biopsy sites with betadine solution. No further treatment was administered. At the time of evaluation, the wether was afebrile. This particular animal is housed with a herd of ∼40 Saanen dairy goats including kids, bucks, wethers, and does in east central Mississippi. There were no signs of trauma to the wether, either to his ear or to any other part of his body, and no abnormalities other than drooping of the left ear and significant edema in the full extent of the ear (Fig. 1). The wether was observed for a 1-month period after removal of ticks and no other clinical signs of disease were observed. None of the other members of the herd displayed similar signs or was observed to have any ticks attached.

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FIG. 1.

Saanen wether with edematous, drooping ear (A) and Gulf Coast tick (Amblyomma maculatum) infestation of left ear (B) demonstrating gotch ear.

Results and Discussion

Two of the three ticks were positive for spotted fever group rickettsiae (SFGR) by PCR of the ompA gene and all three were positive for SFGR by PCR of the 17-kDa antigen gene. An amplicon for the 17-kDa antigen gene from all three ticks was successfully sequenced and showed 100% similarity with the homologous sequence of R. parkeri. Hematoxylin and eosin–stained sections of the ear biopsy specimen showed ulceration and necrosis of the epidermis and diffuse and extensive neutrophilic inflammatory cell infiltrates involving the full thickness of the dermis. These infiltrates were accompanied by necrosis, collections of serum, and occasional extravasated erythrocytes. Some foci of epithelial hyperplasia were also identified at the margins of these infiltrates. No conspicuous bacteria were seen using Warthin-Starry and Lillie-Twort stains. There was no immunohistochemical evidence of SFGR, supporting the hypothesis that gotch ear is not due to rickettsial infection. One month after biopsy, no damage to the cartilage or signs of permanent disfiguration of the ear were appreciated.

Documentation of GCT infestation in cattle causing a condition consistent with the description of gotch ear has been attributed to the presence of large numbers of ticks (Williams et al. 1978), but there has been no description of gotch ear in a goat in the veterinary literature prior to this report. The wether described in this case had only three partially engorged ticks, but none fits the case description of gotch ear (Edwards et al. 2010). Even though the ticks were only partially engorged and lesions at the attachment sites were minimal, the ear was extremely edematous and drooping. Our observations are consistent with Ewing's observation in a dog (Ewing et al. 1997). That animal was part of a human granulocytic ehrlichiosis transmission study in which one of the dogs suffered a severe reaction in the ear described as an inflammatory response and severe edema, which the authors attributed to a reaction from A. maculatum (Ewing et al. 1997). The reaction subsided a few days after tick removal, which is the same pattern observed in the goat in this study. This suggests that gotch ear may occur in both ruminants and nonruminants.