Recent cases of Foot and Mouth Disease (FMD) and Lumpy Skin Disease (LSD) in Indonesia and a FMD outbreak in Bali have put Australia on high alert. An incursion of FMD and LSD would have severe consequences for Australia’s animal health and trade. Severe economic losses would be felt with restrictions being placed on the domestic and international markets for live animals, meat and animal products.
In this case a producer submitted a photograph of a steer with deep ulcers on the nose and lips prompting an emergency animal disease (EAD) exclusion. FMD and LSD were excluded within 24 hours on a weekend.
In August 2022, the Maitland District Veterinarian (DV) was notified of one steer in mob of 30 in the Cooranbong area that had circular epithelial plugs on its muzzle. The plugs fell out when the owner was walking the steer up to the yards, leaving 5-7cm deep holes. The producer said that only one animal was affected. This animal had increased salivation but no sign of lameness. The steer had lost condition over the last 2 weeks and had no noticeable lesions one week prior to contacting the Maitland DV. The steer was isolated from the rest of the herd but was still eating well and did not appear to have any difficulty swallowing. The producer sent a photograph (Figure 1) to the district veterinarian, raising immediate concern for an emergency animal disease. (EAD). An EAD kit was prepared prior to visiting the property and it was explained to the producer that PPE would be worn, and car parked at the gate. Before leaving the office, DPI (Department of Primary Industries) and EMAI (Elizabeth Macarthur Agricultural Institute) were informed of the suspect case and expected samples.
The Lower Hunter had been experiencing above average rainfall and there had been recent flooding in the area. This property had approximately 60 head of mixed breed cattle with no new introductions in the last couple of months. There were no neighbouring cattle, no known pigs in the neighbourhood, no international travel, no international visitors, no international mail and fortunately no other cattle showing clinical signs of LSD or FMD. This steer was in a mob of approximately 30 head. They were in a low-lying paddock with mixed native pasture and had been in this paddock for approximately 1 month.
The 15-month-old steer was lethargic and very easy to handle. The muzzle had 5 circular lesions that varied in size from 0.5cm-5cm diameter and to a depth of approximately 5cm on the edge of the top lip. One of the circular lesions was on the bottom lip. There was a slight increase in drooling, and no lesions on the tongue, gums or dental pad. Slight gingivitis was present around the incisors. The tongue was soft and able to be pulled without any sign of discomfort. There were no lesions around the feet and no sign of lameness. The steer’s temperature was 38.6°C and had a body condition score of 2.
Samples were collected for FMD and LSD exclusion as well as other potential differential diagnosis. The samples that were taken included mouth and nasal swabs in PBGS, blood serum and EDTA, biopsy of the side of one of the ulcers, also one of the epithelial plugs had been collected by the producer and put into a bag and into the fridge. Half the epithelial plug was placed in formalin and half was kept fresh. Also, a faecal sample and hair sample was taken. Producers were advised to remain at the property and to not move any stock.
This case occurred on a Friday, and samples were sent by courier to the Elizabeth Macarthur Agricultural Institute (EMAI) the same day. Within 24 hours LSD and FMD were excluded. Infectious bovine rhinotracheitis (IBR), malignant catarrhal fever (MCF), vesicular stomatitis virus (VSV) and pestivirus were also excluded.
Blood results revealed a mild elevation in GLDH (260 U/L, Normal 0-30 U/L) and AST (279 U/L, Normal 0-129 U/L) suggested hepatocellular injury, and elevated GGT (64 U/L, Normal 0-35 U/L) suggested biliary injury or cholestasis. Fibrinogen and gammaglobulins were also elevated suggesting acute or chronic inflammation.
Skin histopathology revealed dermal and epidermal necrosis which was coagulative, severe, diffuse and sub-acute with dermatitis, lytic necrosis and intralesional bacterial colonies.
There were elements of both lytic and coagulative necrosis. Lytic necrosis is associated with inflammation and bacterial colonies, which most likely represent a secondary infection. However, some colonies are quite deep, so a primary role can not be excluded. Coagulative necrosis is unusual and can be seen with processes such as infarction or thermal/chemical burn. This animal was not in contact with anything caustic or hot, so this can be ruled out.
The DV returned to the property 3 weeks post exclusion to do a follow up liver profile and check the muzzle lesions. GLDH and AST had decreased but the GGT was elevated. A liver fluke antibody ELISA was done and was a strong positive 218 S/P ration (≥150 is considered a 'strong positive' for the presence of Fasciola hepatica antibodies). The lesions on the muzzle were healing well, the steer was eating well and had put on condition. No other animals had shown any lesions.
The producer was not aware of liver fluke on his property, but the wet years that the Hunter region has experienced 2020-2022 have expanded liver fluke distribution in the region. It was recommended that the producer undertake a follow up liver fluke sedimentation test on his herd to see if this animal had been introduced to the property with liver fluke or if it was an issue on this property. Follow up faecal tests demonstrated liver fluke eggs in the herd.
Unfortunately, a definitive diagnosis was not established in this case, but FMD and LSD were excluded along with MCF, IBR, VSV and pestivirus. The epidermal and dermal necrosis produced large circular unusual lesions that could easily be mistaken as a case of Lumpy Skin Disease. Lytic necrosis and deep bacterial colonies could have been related to the wet muddy conditions and coagulative necrosis of the dermis and epidermis could be related to emboli from migration of liver fluke larvae from the gut into the liver.
Liver fluke management on the property was discussed as part of an integrated parasite management approach featuring a mixture of strategic drenches, quarantine drenching cattle from liver fluke areas, and grazing management. Stock will be excluded from the swampy areas of the paddock, which up until this year has not been an issue.
The case was an excellent exercise in investigating a potential EAD. Lessons learnt include the benefit of having a kit/checklist ready to go. No all equipment was taken to the property (including surgical equipment required for the biopsy) necessitating a return to the car, increasing the risk of contamination. The EAD Hotline should have been included in the list of calls. After washing up equipment and myself, I delivered the samples to the courier, went to a car wash and went home to wash myself. I could not return to work, as my office is at the saleyards. This was a very time-consuming job that took the entire day, so it was good to get an understanding of length of time these investigations might take.
EMAI Staff and CSIRO Australian Animal Health Laboratory who aided in prompt reporting back on the EAD exclusion, especially on a Saturday.