2 Nov 2021
Phil Elkins BVM&S, CertAVP(Cattle), MRCVS, provides an overview of primary and multi‑species conditions affecting livestock worldwide, as well as current considerations for keeping them at bay.
Phil Elkins
Job Title
Image © stefanholm / Adobe Stock
As veterinary surgeons, we all graduated with a degree of familiarity with notifiable diseases in the country we graduated in.
In the case of some diseases, such as bTB, a working understanding of legislation and control of the disease is a prerequisite, with industry initiatives such as the TB Advisory Service and further training available supplementing the veterinary industry knowledge.
However, as highlighted in 20161, a working knowledge of the clinical picture presented by other notifiable diseases – in this case lumpy skin disease, with which we may be less familiar – may prove to be extremely beneficial in the case of incursion of an exotic disease.
In fact, the 2001 outbreak of foot‑and‑mouth disease may have been considerably worse were it not for an eagle‑eyed veterinary surgeon identifying suspicious lesions in an abattoir in Essex.
As such, value exists in regularly reviewing the notifiable diseases in species with which veterinarians frequently work.
Certain diseases are designated notifiable – a legal requirement exists to report any suspicion of disease, even without confirmatory tests to the relevant authority (APHA), due to a large potential impact of uncontrolled disease. That impact may be financial, animal health or international trade related, or, in the case of zoonotic disease, human health related. These diseases may also be either endemic (such as bTB) or exotic (such as foot‑and‑mouth disease).
While ultimately the decision to designate a disease as notifiable lies with Defra and its executive agency the APHA, any decisions regarding designation will be carried out in alliance with the World Organisation for Animal Health (OIE). The APHA maintains an excellent resource on notifiable diseases within the UK2.
It is worth reiterating that the primary responsibility for veterinary surgeons with regards to notifiable disease is to report any suspicions to the APHA as soon as they arise and while still on the premises (excluding active surveillance for bTB through intradermal testing). The APHA duty vet will then advise on the next course of action.
The aforementioned bTB is an endemic disease of cattle with serious financial consequences for cattle farmers, veterinary surgeons and the public purse, while also creating a divide between some sections of society.
Control of bTB is through a combination of active surveillance, passive surveillance, movement restrictions and wildlife control. The OV network within the UK will be familiar with much of this.
However, recent times have seen an increase in the advice regarding farm‑specific biosecurity measures and potential introduction of new testing modalities to improve control. Control of bTB deserves a full article in itself and, as such, will be not covered in depth in this article.
BSE has once again reared its head, with a single case in a farm in Somerset. All five cases since 2014 have been identified as part of the active surveillance of fallen stock3.
BSE is a prion disease causing progressive central neurodegeneration, hence earning itself the moniker “mad cow disease”. Clinical signs include progressive altered behaviour – often including aggression and hyperaesthesia, ataxia and weight loss – although they are often non-specific, with animals not generally showing signs until they are older than four years of age.
BSE is believed to have been initially spread through the feeding of meat and bone meal to ruminants, allowing ingestion of the causal prion. Further ingestion by humans is then associated with a similar disease – variant Creutzfeldt‑Jakob disease. BSE control was, therefore, instigated rapidly as a public health concern with large trading effects – many countries refused to import beef or cattle from the UK until the outbreak was proven to be under control.
The recent solitary case has led to China reinstating its ban on British beef (despite not having imported any British beef since lifting the ban), in addition to current bans on Irish and Brazilian beef for similar reasons4.
BSE shows itself as an excellent case study in disease control. A ban on feeding of animal protein to ruminants, together with disposal of specified risk material and movement restrictions on all cattle born before the ban (1 August 1996), has led to near-eradication of the disease from the UK. Active surveillance continues, with sampling of all slaughtered cattle older than 30 months of age and fallen stock older than 48 months (or 24 months if from certain countries).
While clinical signs may be non-specific – and cases very rare – it is worth being aware of the symptoms and notifiable nature of BSE.
The remainder of the cattle‑specific notifiable diseases are currently exotic to the UK. The OIE offers an excellent disease status service – available at https://wahis.oie.int – that shows the current and historic disease distribution of major diseases of international importance. This resource has been consulted with regards to exotic notifiable diseases.
Lumpy skin disease is caused by a poxvirus spread by biting flies and mosquitos, and causes significant economic impact in many countries in which it is endemic.
Typical signs include multiple small (smaller than 3cm) dermal or subdermal firm lesions, primarily around the head and neck (Figure 1), with low to medium morbidity and very low mortality. Associated signs include malaise, ocular and nasal discharge, and fever5.
Lumpy skin disease is widespread throughout Africa, Asia, eastern and south‑eastern Europe, and the Middle East. Given the changing distribution of vectors and other vector‑borne diseases, the risk to the UK of lumpy skin disease is genuine, despite it never presenting in the UK historically.
Enzootic bovine leukosis was last seen in the UK in 1996 – and with current outbreaks in the Middle East, south-east Asia and southern Africa, the risk to the UK is low.
EBL is caused by the bovine leukaemia virus, unlike the clinically indistinguishable sporadic bovine leukosis. The causal virus is believed to be primarily spread via unhygienic processes involving exposure to blood products, such as tattooing, rectal palpation and dehorning.
The clinical picture is highly variable, with signs associated with the sites affected by lymphosarcomas including lymphadenopathy, pain and physical consequences of the enlargements – altered movements, intestinal obstruction or liver failure, for example.
Contagious bovine pleuropneumonia – caused by Mycoplasma mycoides subspecies mycoides – was the cause of one of the first great cattle plagues, but hasn’t been seen in the UK for more than 100 years, or Europe for 20 years. Five outbreaks exist in northern Africa and the risk to the UK is extremely low.
Warble fly is notifiable in Scotland only and has been eradicated from most of the world – except a small pocket in northern Africa – through the widespread use of avermectins.
Rinderpest has been globally eradicated and is now limited to laboratory samples only.
The UK has historically suffered occasional outbreaks or individual cases of anthrax in the cattle population, with the last confirmed case in 2015.
Anthrax can affect many species of mammal and bird, and is most commonly associated with sudden death. Any death without preceding clinical signs should be reported to the APHA, which will decide if an anthrax test is required consisting of a peripheral blood smear. Until that point, it is important that the animal is not moved to allow suitable cleansing, disinfecting and disposal should the animal test positive.
Anthrax is cause by Bacillus anthracis, a soil‑borne bacteria that can survive for decades in the soil; therefore, continued vigilance is important. Anthrax is zoonotic.
Many species of Brucella exist that affect different species – brucellosis in cattle is associated with abortion and premature births.
It is also zoonotic, causing “undulent fever” in humans, with infection common in veterinary surgeons before the introduction of disease control in cattle and the use of rectal gloves.
The UK has been officially brucellosis free since 2004; however, surveillance measures remain: regular testing of bulk milk samples occurs and any abortion should be reported to the APHA, which will make a risk‑based assessment on whether further sampling is required.
Although many countries are still working towards official eradication, no current ongoing outbreaks exist following resolution of outbreaks in central Europe in 2013.
Bluetongue virus was historically restricted to tropical and subtropical areas; however, with the spreading distribution of the Culicoides midge vector, outbreaks have increased in recent years – including the serotype 8 outbreak in Europe in 2006‑8.
A total of 27 different identified serotypes exist, all showing differences in virility and pathogenicity. Bluetongue primarily affects cattle and sheep, causing lesions of the mucous membranes.
In cattle, the clinical presentation includes a high fever (higher than 40°C), with nasal and ocular discharge, swelling of the head and neck, oral ulceration and associated salivation, and teat swelling.
Important differentials include foot‑and‑mouth disease (see below), infectious bovine rhinotracheitis and malignant catarrhal fever. Some cases present as clinically indistinguishable from some endemic disease and any suspicions should be reported for further investigation.
As spread is via midges, the main risk period is when weather patterns encourage both midge spread from the continent and midge survival; as such, summer and autumn would be the main periods.
Central Europe continues to be affected by bluetongue, with nearly 200 outbreaks reported in 2021 to date.
The 2001 foot‑and‑mouth disease outbreak in the UK will live long in the memory of those vets and farmers affected (as will the 1967 outbreak).
A disease of cloven‑hooved animals, foot‑and‑mouth disease is characterised by high morbidity with severe disease, with disastrous consequences for animal welfare.
As the disease is highly contagious, a large amount of disease spread occurred between the first animal being infected and control measures being instigated. Continued vigilance is essential to minimise the consequences should the virus re‑enter the UK.
Affected cows develop vesicles – that burst to create ulcers – in the mouth, and on the tongue and feet. This can lead to associated milk drop, fever and lameness.
Any cow with multiple ulcers on the feet or mouth should be reported to the APHA.
The two most recent outbreaks of foot‑and‑mouth disease in the UK were traced back to imported meat fed to animals. This practice is now illegal and, as such, the risk of incursion reduces, although ongoing outbreaks exist throughout Africa and Asia (including Turkey).
Vesicular stomatitis can present similarly to foot‑and‑mouth disease, with vesicles and ulceration of the mouth, coronary band and teats. It is vector-borne and is restricted to the Americas.
Rift Valley fever and surra are diseases that affect cattle along with other species. They are both restricted to Africa, having never been reported in the UK, with no realistic likelihood of incursion happening in the foreseeable future.
A number of notifiable diseases exist that can affect cattle, but for which the primary host is another species. These are listed in Panel 1.
Aujeszky’s disease is currently active in France, while the remainder of the diseases have a distribution that makes incursion in cattle unlikely (rabies is present in the UK, but only in the bat population).
In summary, awareness of the notifiable disease of cattle is essential as part of the surveillance network in the UK.
