INFLUENZA: At the Human-Animal Interface

Greater Kashmir

Better communication and collaboration between medical doctors, veterinarians and scientists in tackling zoonotic diseases like Influenza that are shared by humans and animals, is the need of the hour

3rd swine flu death in Delhi, cases rise to 36 (Greater Kashmir: 10 January, 2015). As per the report, a total of 36 persons were tested positive for the virus in January alone, four more than the total number of cases recorded in entire 2014 in the city. The disease had reared its head in 2009 and till May 2010 as many as 1035 people had died of the disease in India and more than 10,000 were infected.  Earlier owing to rising swine flu cases across the country, in the Kashmir Valley Doctors Association Kashmir (DAK) had sounded a warning: “DAK sounds alert, Kashmir not prepared to combat it” (GK: 04/01/2015). As per DAK, Kashmir hospitals are not prepared to combat Swine flu and the two designated hospitals, SKIMS and SMHS do not have the facility of negative pressure isolation wards for HINI patients. Tamiflu (Oseltamivir), the only drug used for treatment and prophylaxis of H1N1 is not stockpiled in the valley. There are no Swine flu vaccines available in the valley to be given to the high risk persons as the virus in them can be fatal.

Any disease or infection that is naturally transmissible from vertebrate animals to humans and vice versa is classified as a zoonosis. Zoonoses have been recognized for many centuries, and over 200 have been described. They are caused by all types of pathogenic agents, including bacteria, parasites, fungi and viruses. Human health is inextricably linked to animal health and in fact sound human health is subservient to sound and healthy animals. About 75% of the new emerging diseases that have affected humans over the past 10 years have been caused by pathogens originating from animals or from products of animal origin. Many of these diseases have the potential to spread through various means over long distances and to become global problems. Reducing public health risks from zoonoses at the human-animal interface is not easy and straightforward. Management and reduction of these risks must consider the complexity of interactions among humans, animals and the various environments they live in.

Influenza virus belongs to family Orthomyxoviridae and comprises of 3 genera Influenzavirus A, Influenzavirus B and Influenzavirus C. All the 3 types occur in humans, whereas in animals only Influenzavirus A is of major concern as cause of natural disease. In animals the viruses cause equine, swine and avian influenza; among them swine and avian influenza being of zoonotic importance. The enveloped single stranded-RNA virus is covered by 2 types of glycoprotein spikes known as peplomers: Neuraminidase (N) and Hemagglutinins (H). There are 15 Hemagglutinin and 9 Neuraminidase types and these glycoproteins determine the subtype of the influenza virus. Though the sub types H1N1 and H3N2 affect Swine, H5N2 and H7N1 affect avians, whereas H1N1, H3N2, H2N2 and H5N1 affect humans. Apart from different variants of glycoprotein, the viral RNA genome is also divided into 8 or 7 segments. The peculiarity of Influenza viruses is their ability to quickly transform owing to genomic recombination and reassortment among different species and viruses by way of antigenic shift and drift, thereby giving rise to new variants. This variation poses problems in prevention and control by vaccination as the new variants keep on emerging, making influenza deadly dangerous.

The influenza viruses have undergone major genetic changes, resulting in global pandemics and large tolls in terms of both disease and deaths. The most infamous pandemic was “Spanish Flu” which affected large parts of the world population and is thought to have killed at least 40 million people in 1918-1919, more than the causalities caused by the infamous World War-I. More recently, two other influenza A pandemics occurred in 1957 (“Asian influenza”) and 1968 (“Hong Kong influenza”) and caused significant morbidity and mortality globally.  Apart from causing innumerable human deaths, influenza viruses have taken a heavy toll on animals and birds wherein on one hand millions of birds naturally died due to the disease and on the other hand millions were culled, causing huge economic losses. Further, Influenza also poses a threat to the global trade of birds and animals among different countries. Thus, Influenza is a cause of concern for medical doctors as well as veterinarians.
Among animals, avian and swine influenza are important as they are transmitted to humans owing to contact with birds and pigs. Wild aquatic birds like ducks, geese and gulls show milder forms of the disease and act as carriers of avian influenza virus. But they cause heavy mortality in domestic poultry birds when the latter acquire the infection and then the virus can be subsequently transmitted to the humans. Most human contractions of the avian flu are a result of either handling dead infected birds or from contact with infected fluids of these birds. Influenza is quite common in pigs. Pigs are unusual as they can be infected with influenza strains that usually infect three different species: pigs, birds and humans. This makes pig a host where influenza viruses might exchange genes, producing new and dangerous strains. The main route of transmission is through direct contact between infected and uninfected animals. Airborne transmission through the aerosols produced by pigs coughing or sneezing is also an important means of infection. The transmission from swine to humans is believed to occur mainly in swine farms where farmers are in close contact with live pigs.
Swine flu in humans spreads quickly in comparison to bird flu, but casualty is lesser in swine flu than bird flu. The bird flu virus affects all systems of human body, but the swine flu virus affects mainly the respiratory system. The characteristic symptoms of Human Influenza are fever, cough, sore throat and body aches. Symptoms may last for one-two weeks. Additionally, Nausea, vomiting, diarrhea and rashes may also occur. Precautions include adherence to cough and respiratory hygiene, washing hands regularly, avoiding touching face, mouth and nose with dirty hands. Patients, who have symptoms, should stay indoors and avoid crowded places. Influenza can be tackled in humans by restricting the transmission of virus between animals to humans by culling of infected livestock and proper disposal of carcasses, proper vaccinations, use of certain antiviral drugs like Oseltamivir (Tamiflu) or Zanamivir (Relenza), symptomatic treatment, immune system enhancement and other supportive therapies to curb secondary infections.

The idea that by working together medical doctors, vets and scientists can do more to tackle the health challenges facing the world than they can ever achieve separately continues to gather momentum.  The concept has been termed as “One World, One Health, and One Medicine”. Since most of the new and emerging infectious diseases affecting humans originate in animals, it looks specifically at how efforts at the interface between human and veterinary medicine can be improved.  It makes the point that pathogens circulating in animal populations can threaten both animal and human health, and thus both the animal and human health sectors have a stake in and responsibility for their control. It calls for a joint framework to address gaps and strengthen collaboration in the activities of human and animal health laboratories and to promote cooperation between human and animal surveillance systems. It says that models for forecasting animal disease outbreaks should be developed in close collaboration so that animal disease outbreaks which precede human outbreaks can provide an early warning and ensure preparedness and a targeted response. 

Author is an alumnus of Faculty of Veterinary Science, SKUAST-K