How African Swine Fever can affect humans


By Dr Milton Lum

The spectre of African Swine Fever (ASF) rose its head in Sarawak recently when one out of 17 samples of canned pork luncheon meat imported from China was found to contain the ASF DNA.

While the state’s pigs are currently still clear of ASF infection, outbreaks of this zoonotic disease have occurred in neighbouring countries Vietnam, Laos, Cambodia, Myanmar and the Philippines, as well as China and other Asian and Eastern Europe countries.

The situation in China is particularly serious with millions of pigs having died or culled this year.

ASF is caused by a DNA virus and is a very contagious haemorrhagic disease that affects pigs exclusively.

It causes malaise, fever, vomiting, bloody diarrhoea, disseminated intravascular coagulation (where blood clots develop abnormally in the bloodstream) and death in both wild and domestic pigs.

Domestic pigs are more vulnerable to the disease, with their death rate being nearly 100% in most outbreaks.

The virus passes between pigs via direct contact, contact with contaminated feed or contact with vectors like ticks.

The ASF is a hardy virus that remains stable and infectious for three to six months in uncooked pork products.

It is not known to infect humans or other animals.

ASF was first reported in Kenya and has remained in Africa for much of its history.

However, ASF surfaced in Georgia in 2007 and has spread from the Caucasus to Eastern Europe, affecting both the domestic pig and wild boar populations.

Pork is the second most commonly consumed meat in the world, comprising more than a third of global consumption.

With increasing meat demand, the demand for pigs has also increased as they are able to convert low quality feed to protein efficiently.

About half of the over one billion pigs in the world are found in China, where they are used mostly for domestic consumption.

Countries with a local outbreak of ASF usually use culling of the affected or potentially affected animals, along with sanitary disposal of the carcasses, as the main method of controlling the outbreak.

The United Nations Food and Agricultural Organization (FAO) stated that ASF is endemic (entrenched) in the Xinjiang and Tibet regions, making its eradication more difficult.

The FAO also estimated that about one-fifth of China’s pig population may have been culled in the first few months of 2019.

There is currently no vaccine for the prevention of ASF, neither is there treatment for infected animals.

The ASF outbreaks do not just affect the pig industry, but also have effects on human health and healthcare.ASF and heparin

Heparin, a blood-thinning drug (anticoagulant), is prescribed to people at risk of developing blood clots, which can block blood flow or travel to the lungs or brain.

Blood clots that travel to the lungs or brain can cause a pulmonary embolism or stroke respectively, which can be life-threatening.

Heparin is used in the treatment of venous thromboembolism; prophylaxis in medical and surgical practice, e.g. for the prevention of heart attacks and stroke; and in various medical interventions, e.g. blood transfusion, maintenance of patency in central vascular devices, haemodialysis, angiography and percutaneous coronary intervention (PCI or angioplasty).

Heparin may be prescribed for the short or long term depending on the patient’s clinical condition.

The action of anticoagulants may need to be reversed when there is active bleeding during their use or when the indication for anticoagulation is no longer present.

One of the advantages of the common form of heparin is that its effects can be neutralised or reversed rapidly by specific drugs.

In contrast, there is no antidote for the synthetic heparin available in Malaysia.

The active ingredient in commercially-available heparin in many countries is from pig intestines.

Cows were previously a source of heparin, but the use of such products were discontinued in the 1990s, due to concerns about the prions that cause mad-cow disease.

Another potential source of heparin is from sheep or goats, but these products have not been tested in humans.

China, which is the world’s largest pig producer, accounts for about 60-80% of the global supply of the active pharmaceutical ingredient (API) needed in the manufacture of heparin.

While culling is effective in containing the spread of ASF, the measure has serious implications for the manufacturing of heparin, leading to a potential global shortage of this drug.

Fresenius Kabi, a major global heparin manufacturer, stated "... we do not rely solely on China for API.

"We source from multiple suppliers and geographies to serve our customers, but the situation in China is expected to cause API supply constraints globally for an unknown period.

"As mentioned above, the market is also experiencing finished pro-duct supply interruptions from other manufacturers.

"This has significantly increased demand for Fresenius Kabi heparin.

"As a leader in injectable medications and a leading supplier of heparin, Fresenius Kabi has put plans in place to monitor the market and to help mitigate a potential future heparin shortage."No viable alternatives

The global pharmaceutical supply chain requires a stable supply of raw ingredients for manufacturing and finishing facilities in many countries.

This complex and integrated system is very dependent on ingredients and products from far-off countries, and is highly vulnerable to disruptions in the supply of raw ingredients.

Supply disruptions due to a loss of production capacity can be mitigated by increasing production at other facilities or sourcing new suppliers.

However, for heparin, the issue is not production capacity, but the supply of API.

There is currently no apparent viable replacement for the API from China.

Considerable time and effort would be needed for clinical trials for new heparin products and/or to develop safe and effective protocols that address safety concerns about bovine-based heparin.

Although there are ongoing efforts to produce synthetic heparin API, more work is required.

The alternative anticoagulant drugs currently available may not be suitable replacements in all patients and clinical situations.

Some experts believe it may take years to control the ASF outbreaks.

Even if the outbreaks were brought under control soon, it would take time for the pig industry in China to recover.

This could mean a prolonged shortage of heparin that would impact on its usage.

The current ASF outbreaks pose no direct threat to human health.

However, the threat to humans stems from the impact of the control measures, i.e. the unprecedented culling.

With China’s efforts to control ASF, the production capacity for heparin will be limited to some extent for an unknown period.

Addressing ASF’s impact on human health and healthcare goes beyond the checking of imported food products or pigs for ASF.

Although regulators in many countries are monitoring the heparin supplies, there is no information as to whether the Health Ministry is doing likewise.

Furthermore, public disclosure by the ministry of its policies and protocols to mitigate the potential effect of ASF on human healthcare would go a long way in providing direction for hospitals and medical practitioners, as the availability of heparin would certainly impact on the safety and quality of care.

The reader is advised to discuss with their attending doctor on the types, risks, benefits, effectiveness and side effects of heparin, which should include reversal or neutralisation if active bleeding ensues after injection.

In addition, the availability and feasibility, e.g. costs, are other important factors to consider.

The stopping of heparin therapy should only be on medical advice.

(The Star/Asia News Network)

Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. The views expressed do not represent that of organisations that the writer is associated with.

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