Many dairy owners and dairy practitioners are aware of wooden tongue as a problem from time to time in individual cattle. However, the instances of outbreak forms of this disease are few. This case outlines the coming together of a number of factors to result in an outbreak of wooden tongue in this dairy herd (both the steers and heifers).
On 22/3/12, 11 out of 81 head of dairy heifers were noted to be drooling severely and showing signs of bottle jaw (Figure 1) to varying degrees. In the previous 3 weeks, 5 animals were treated in the steers for a similar condition which was presumed to be wooden tongue. Both the owner and the dairy consultant had never seen such numbers of animals showing wooden tongue so were concerned that perhaps there was another cause.
Clinical examination of the heifers most affected showed severe thick salivation evident at rest. Large swellings in the submandibular region with some being soft and fluid filled and others appearing to be more discreet palpable nodules. Temperatures ranged from 38.3-38.7 Celcius in animals examined. The animals were generally bright and alert and in some cases appeared to be hyperexciteable. On palpation of the oral cavity, no sign of erosions present but the majority of animals showed tooth eruption with damage to the mucosa around the eruption site. The tongues were generally enlarged and thickened at the junction between the torus and apex. Two of the animals examined showed a thick yellow nasal discharge but had no lesions in the nasal cavity or other respiratory signs.
Laboratory testing found samples to be negative for BVDV (antibody AgID negative), negative for liver fluke ELISA, and 2/3 were positive for BRSV antibody ELISA. Magnesium levels were all at the low end of normal (0.89-0.92 mmol/L versus the range of 0.74-1.44mmol/L).
Wooden Tongue (Actinobacillus lignieresii) typically affects individual cattle causing acute symptoms of excess salivation, difficult mastication and inappetance. There can also be accompanying swelling in the affected area, under the jaw and in the regional lymph nodes. Infection is thought to occur via trauma to the oral mucosa when grazing rough feeds (weedy hay/silage; straw or soil-contaminated silage). However, it has been reported as outbreaks in at least two cases (see references below).
In this case, the most recent paddock feed was a lucerne / clover/ grass based pasture that was not particularly weedy or rough. Flooding in these paddocks had occurred in recent months with the high rainfall. The producer was fairly confident it was wooden tongue with the first few early cases but became concerned when additional cases also started appearing and in a different mob. Also the typical tongue out appearance that had been seen before was not evident in these heifers. They presented with the excessive salivation and submandibular swellings with the tongues still being quite mobile.
The BRSV positive titres may have affected the overall herd immunity; combined with the tooth eruption of this age group and the grazing on recently flooded pastures, the end result was an outbreak of Wooden Tongue.
Animals were treated with penicillin in less affected animals and at least two were given sodium iodide to combat the more severe swelling of the jaw and tongue. There was a good response to treatment.