CASE NOTES
Two "Outbreaks" of Actinobacillosis in beef cattle
Megan Davies, DV Narrabri
Posted Flock & Herd September 2015
Introduction
Actinobacillosis, or Wooden Tongue is not an uncommon condition in cattle, but is generally seen sporadically in individual animals. It does not spread readily unless predisposing environmental conditions cause a high incidence of oral lacerations (Radostits et al. 1994). In the following cases, signalment, diet and environmental conditions combined to cause outbreaks of the condition within these herds.
Case 1
A landholder reported cattle with excessive drooling, bottle jaw and open lesions around the jaw and neck on an extensive grazing property in Burren Junction, North Western NSW. Approximately 50 animals were affected in a mob of 500 Angus steers and heifers (Figures 1, 2 & 3).
Figures 1, 2 & 3 — young cattle with submandibular swelling and masses
The cattle were aged 1-3 years and had been grazing oat stubble for the past three weeks, during which time the problem had noticeably worsened. Prior to the oats, they had been grazing 3 year old wheat stubble, and had been early weaned due to prolonged drought conditions on the property. They had been vaccinated with 5-in-1 at weaning, and had not been recently wormed.
The worst affected animals were standing with necks outstretched, drooling, with stridor and heavy breathing. Multiple animals had large nodular masses evident, predominantly under the jaw, but some animals also had masses protruding from their flanks (See figure 4), and one had a large mass in the inguinal region.
Figure 4: Affected steer with flank lesion
Examination of the worst affected animals showed large, firm granulomatous masses in predominantly submandibular locations. The masses ranged from 5-15cm diameter, and were not attached to bone. Some were open with a bloody or purulent discharge (See figure 5), while others were closed, with no sign of external injury.
Figure 5: Affected steer with open lesion
Most affected animals also had some degree of subcutaneous oedema in the neck. Affected cattle had elevated temperatures, ranging from 39.5°C to 40.6°C, and several were found to have open wounds in their mouth due to the eruption of their adult incisor teeth (Figure 6). Several animals had mild swelling of the tongue and reduced muscle tone (Figure 7), causing the tongue to protrude. One animal was observed to have a small (5cm diameter) granulomatous mass under the tongue (figure 8).
Figure 6: Erupting adult incisors in affected animal
Figure 7: Affected Steer with protruding tongue
Figure 8, Lesion under tongue of affected animal
Biopsies collected from several animals were sent to EMAI for testing (Figure 9) and returned a pure growth of Actinobacillus lignieresii. Histopathology reported Lymphadenitis, granulomatous, multifocal, chronic, and severe with intralesional Splendore-hoeppli material. Biochemistry on two affected animals showed one had a mild copper deficiency (7.3umol/L, range 9-20umol/L), however subsequent testing on 9 other affected animals showed copper levels within normal limits. Antibiotic sensitivity testing of the cultured bacteria revealed sensitivity to a range of common antibiotics including tetracyclines.
Figure 9: Granulomatous lesion removed for laboratory testing
The affected animals were treated with long acting oxytetracycline and removed from the oat crop. The situation resolved to a point that affected animals were no longer easily identifiable in the paddock.
Case 2
Six months later on a nearby property at Burren Junction, 15 Angus x Hereford cows in a mob of 40 with calves at foot were observed with similar lesions. The landholder reported “bottle jaw” and firm round masses near the jaw. The cattle were being fed oaten hay from hay feeders in a paddock, with access to sparse pasture - this property was also affected by long term drought.
On examination, the affected cows were found to have 5-15cm diameter granulomatous lesions in the submandibular region. Two cows also had moderate swelling of the caudal tongue. None were observed to have lesions within the oral cavity. Their body temperatures were all within the normal range, and none had been reported to have lost weight (BCS 2/5). Faecal testing for worm eggs revealed no significant worm burden.
A diagnosis of wooden tongue was made based on clinical signs, and the affected cows were treated with a single long acting Oxytetracycline injection.
Treatment
The recommended treatment of sodium iodide was prohibitively expensive in these cases. Broad spectrum long acting antibiotics were a more feasible and practical option. The bacteria is reported to survive for up to 5 days in the environment (Radostitis et al., 1994), therefore in both cases it was recommended that affected cattle be removed from the rest of the herd to avoid further contamination of the paddock and feed bins.
Routine management advice was also given including recommendations to wormtest and drench if required. AD&E injections were also recommended due to the prolonged dry and lack of green feed available.
Discussion
Actinobacillus lignieresii is a normal inhabitant of the oral cavity and rumen (Radostits et al. 1994), and infection occurs due to damage to the oral mucosa. Abbatoir surveys suggest that subclinical infections are common, particularly affecting the draining lymph nodes of the head (Radostits et al. 1994).
Actinobacillosis is a common diagnosis in cattle, but generally affects individual animals - it unusual to see such high numbers affected within a herd. Both of these herds were subject to considerable stresses, both nutritionally due to prolonged drought, and physiologically, with one mob teething, and the other with young calves at foot. It is likely that this contributed to the "outbreaks" in these cases.
Interestingly, both herds were eating oats - stubble and hay - and we had further anecdotal reports from other landholders around the same time of cattle on oat stubble being affected with suspected wooden tongue. Parkinson et al. (2010) reports a higher incidence of disease in cattle feeding on crops with awns, such as oats, and Jubb et al. (2007) reports that the common primary lesion is caused by grass seeds and awns stuck in the lingual groove. The eruption of teeth also commonly causes an entry point for the bacteria (Jubb et al. 2007).
Actinobacillosis is a disease of soft tissue, spreading as a lymphangitis involving regional lymph nodes, differentiating it from actinomycosis, which causes bone lesions. The retropharyngeal and submaxillary lymph nodes are most commonly affected, which causes dysphagia and dyspnoea (Jubb et al., 2007).
Other differentials we considered were foreign bodies, grass seed abscesses, intestinal worms, Actinomycosis, granulomas and neoplastic growths. Exotic diseases that cause excessive salivation such as foot-and-mouth and bluetongue were also excluded based on clinical examination.
Cutaneous Actinobacillosis is reportedly uncommon, presenting as lesions on the flanks and thighs in the form of large ulcers or nodules which may exude pus (Radostits et al. 1994). We are unsure why the cattle on the first property presented with the cutaneous form in this instance.
Treatment recommendations vary, with reports of spontaneous recovery in untreated animals (Radostits et al. 1994). Intravenous Sodium Iodide is recommended, but was prohibitively expensive in this case ($150 per dose). Most broad spectrum antibiotics are effective (Parkinson et al. 2010), and sensitivity testing confirmed that tetracyclines were likely to be effective against the causative agent in this case.
Response to treatment is generally good, but recurrence is common, particularly in chronic cases (Radostits et al. 1994). It is difficult to prevent the disease except through minimising exposure to rough or spiky feedstuffs (Parkinson et al. 2010), which can prove difficult under drought conditions.
Actinobacillosis is not considered a high risk zoonotic disease, but the organism has been isolated from bite wounds inflected by cattle (Radostits et al. 1994), so care should be taken when investigating these cases.
References
- Jubb, Kennedy & Palmer (2007) Pathology of Domestic Animals 5th Edition. Volume 2. Saunders Elsevier, Sydney
- Parkinson TJ, Vermunt JJ & Malmo J (2010). Diseases of Cattle in Australasia. A Comprehensive textbook. Vetlearn, 2010
- Radostits OM, Blood DC & Gay CC (1994). Veterinary Medicine. A Textbook of the diseases of Cattle, Sheep, Pigs, Goats and Horses. 8th Ed. Bailliere Tindall, Sydney