Sustainable strategy to eliminate vector-borne diseases

by Shubho Roy and Smriti Sharma.

In his budget speech of 2017, the Finance Minister Arun Jaitley announced that the government has prepared an action plan to eliminate two vector-borne diseases by the end of this year (Paragraph 64):

"Poverty is usually associated with poor health. It is the poor who suffer the maximum from various chronic diseases. Government has therefore prepared an action plan to eliminate Kala-Azar and Filariasis by 2017..."

Kala Azar, also known as Visceral leishmaniasis, is caused by a protozoan parasite of the Leishmania genus. It is carried by an insect vector: Sandfly. If left untreated, Kala Azar can lead to the death of the patient.

Filariasis is a painful disfiguring disease which is caused by roundworms of the Filarioidea superfamily. It is carried by a mosquito vector: Culex quinquefasciatus. The most disturbing symptom is elephantiasis where the patients body parts swell to massive proportions. The infection generally occurs during childhood but manifests itself later in life and can lead to permanent disability.

In this article, we analyse this announcement. We argue that eliminating vector-borne diseases is a good cause for health policy to pursue. However, there is a need to place these actions within a larger strategy on communicable and vector-borne diseases. The critical component of that, which is at present lacking in India, is a sound surveillance system.

Communicable diseases in health policy

A lot of what governments do in the field of health is of dubious value. Tackling communicable diseases, like Kala-Azar and Filariasis, however passes the basic tests of public economics (Hammer, 2015). Communicable diseases involve a market failure, an externality. When one person gets infected, not only does that person suffer, there is the possibility of others getting infected. This is a negative externality. Each person will under-spend on preventing or curing the disease as the individual does not price the adverse impact upon others. This creates a market failure and justifies a role for the State.

In the extreme, when we get to eradication, we get to a public good. When a communicable disease is eliminated, everyone is protected, even if they did not pay for it. It fits both the tests of a public good:

1. non-excludable: it is not possible to prevent consumers who have not paid for it from having access to it. There is no way to ensure that only the people who paid to eliminate Kala Azar don't get Kala Azar and others are still exposed to it.
   
2. non-rivalrous: it may be consumed by one consumer without preventing simultaneous consumption by others. When an infectious disease is eliminated, it cannot come back. Enjoying good health by some persons does not reduce the supply of good health, i.e. absence of the disease.
   

Why Kala Azar and Filariasis?

But we must ask: Why were Kala Azar and Filariasis prioritised for elimination in the Budget speech?

It is not because they are most widespread diseases in the country. Statistics from the Directorate of National Vector Borne Disease Control Programme (NVBDCP) (Table 1) show that here are other vector-borne diseases like Malaria, Dengue and Chikungunya which are more important.

Table 1: Magnitude of vector-borne diseases in India (2014)

Disease	Cases in 2014	Deaths in 2014
Malaria	1,102,205	562
Dengue	40,571	137
Chikungunya	16,049	Unavailable
Encephalitis (Japanese and Acute)	12,528	2,084
Kala Azar	9,241	11
Filariasis	Unavailable	Unavailable

Perhaps it is felt that these diseases are low hanging fruits. Kala Azar is restricted to four states while other vector borne diseases are everywhere. In 2014, a new drug liposomal amphotericin was found to cure Kala Azar with a single dose. Previously, a course of 28 daily doses with hospitalisation was required.In the case of Filariasis, India has reduced the national microfilaria rate (based on sample blood tests) from 1.24% in 2004 to 0.44% in 2014. In Goa, Daman & Diu and Pondicherry, the rates have fallen low enough that mass drug administration (the standard treatment methodology) was stopped in 2012. The government has also achieved good coverage under Mass Drug Administration with 85.6% of the population covered in 2014.

Choosing low hanging fruits has its virtues. It allows for quick results and can potentially help create State capacity. There is a unique charm to eradication. Once a communicable disease is eradicated, you do not have to work on it again (apart from some low-level continued surveillance to check for recurrence). This frees up resources for other purposes.

A story of failure

In the recent past, India has seen many outbreaks of re-emerging infections, which were claimed to be eliminated. Kala Azar itself reemerged after near eradication in the 1960s. DDT was used for controlling malaria between 1953-64. This helped to decimate the sand-flies that cause Kala Azar. But the pathogen continued to reside in humans. In 1977, when the sand-flies resurged, Kala Azar resurfaced. The disease again resurged in 1983 and 2003 (Muniaraj, 2014). The National Health Policy of 2002 had envisaged elimination of Kala Azar and Filariasis by 2010. This was postponed to 2015.The plague in Surat in 1994 was followed by an outbreak of pneumonic plague in Himachal Pradesh in 2002 (Joshi et al., 2009). There was another bout of plague in Uttarkashi in 2004 (Mittal et. al., 2004). The first outbreak of Chikungunya in India was reported in 1963 but it resurged after three decades in 2006.

What does it take to finish the job?

It is important to ensure that an elimination drive is sustained beyond its stated date. Vector-borne diseases will not cease to exist with the administration of mass dosage of drugs alone. We need continued disease surveillance and epidemiological investigation post-2017 too. A Kala Azar patient can relapse after six months after the end of treatment. Similarly, Filariasis does not manifest itself in early stages in any outward symptoms. The infected person can thus continue to host the disease for several years.

India is at the cusp of eliminating Kala Azar and Filariasis. It must ensure that the eliminated diseases do not re-emerge. This requires a surveillance system. Surveillance can provide information on entomological data, which can help in creating clusters of diseases that can be targeted by similar vector management measures. Surveillance for epidemiological data can help in calculating the disease burden attributable to each disease. Lastly, surveillance can provide information on implementation. This can help in monitoring and evaluation of disease control and prevention.

Prevention, control and surveillance: current scenario

NVBDCP's present strategy concentrates on vector management by using indoor residual spraying, nets impregnated with insecticides and anti-larval measures. In addition, early diagnosis and complete treatment is provided to afflicted patients. NVBDCP frames technical guidelines and policies to guide States for implementation. Health departments are responsible for the prevention and control of vector-borne diseases at the State level. But their approach to vector-borne diseases continues to be ancillary and ad hoc in absence of entomological and epidemiological data, and data dissemination:

• Poor entomological surveillance: The government established 72 zonal Malaria offices to conduct entomological surveillance but only 50% of these are functional. State health departments conduct larval surveys but they do not count adult mosquito populations. The field staff uses the outdated ladle and dip method for studying the vector population, despite the availability of new and improved devices like ovitraps. Vector management efforts employ fogging and anti-larval activities to contain mosquito populations. But, this is done without adequate evidence on vector populations.
  
• Poor epidemiological surveillance: IDSP has a laboratory network of 117 district labs in 28 States/UTs to perform tests for epidemic-prone diseases. Out of the 117 laboratories, 44% of the laboratories do not conduct all the tests recommended under IDSP. This means that some diseases cannot be confirmed and therefore they remain unreported. Private healthcare providers do not report diseases and that leads to under-estimation of the disease incidence. The data for dengue, Kala Azar and Chikungunya on NVBDCP's website is outdated enough to render it useful for public health management. Case and death data for filariasis is unavailable.
  
• Poor data collection and dissemination: The reports from the rural reporting units to District Surveillance Units of IDSP are often delayed. While 85% districts communicate surveillance data through emails, 67% report data through the portal. This leads to delays in collating and analysing data. State health departments campaign, educate and inform the public about the diseases. But, none of the measures taken by State health departments are ever evaluated for their impact.
  

The information from NVDCP has three groups of problems:

1. Missing data: The epidemiological data for some diseases is either incomplete or missing. The missing data on deaths cannot be construed as zero deaths.
   
2. Policy decisions without evidence: India hopes to eliminate Filariasis by the end of 2017. But there is no data on the number of cases and deaths resulting from Filariasis.
   
3. Under-estimation of incidence: The burden of disease is likely to be highly under-stated by the official statistics. As an example, Dhingra et. al., 2010 estimate that Malaria kills between 125,000 and 277,000 persons in India every year. This is vastly unlike the official statistics. Similarly, Haanshus et. al., 2016 find that in the class of hospitalised patients with undifferentiated fever in India, malaria prevalence is as high as 19%. Similarly, Shepard et. al., 2014 estimate there were 5.8 million cases of dengue per year.
   

Building a surveillance system

A sustainable strategy should bring down the infectious diseases in the short term and avoid resurgence later on. The US Centers for Disease Control and Prevention (CDC) has developed a framework for preventing infectious diseases which focuses on:

• Continued surveillance of infectious diseases, laboratory detection and epidemiological investigation;
  
• Reducing diseases by developing vaccines, preparing strategies for infection control and treatment;
  
• Using scientific data to inform health policies to prevent and control infectious diseases.
  

India requires the development of similar principles. We need a robust surveillance system that measures all vector-borne and communicable diseases. This system should generate a constant stream of good quality data which can feed back into management decisions in public health.

The policy agenda for vector borne diseases involves the following components:

• Building entomological surveillance capabilities: State health departments should invest in their entomological surveillance capabilities. They should systematically collect and document changes in vector occurrence, abundance and infection rate for the entire country. State health departments should complement larval surveys with adult surveys. In order to estimate and monitor adult mosquito prevalence, health departments should procure mosquito traps like ovitraps and BG-Sentinel traps (Sivagnaname and Gunasekaran, 2012). State health departments should make the entomological surveys public. For example, the Health Department of New York has launched interactive maps. These maps show the progress made on mosquito surveillance and control operations. The City of Chicago publishes maps with a list of locations and mosquito test results. The CDC displays information on vector borne diseases in maps which also give information on the vectors for each disease.
  
• Improving epidemiological surveillance: The government should assess the disease burden for each vector-borne disease. State health departments collect information on disease incidence and mortality. The epidemiological surveillance should also include information on geographical distribution of the disease and sub-populations affected. This information should be compiled and made publicly available. Better laboratories are required that conduct tests for all the vector-borne diseases.
  
• Improving data collection and dissemination: The government should strengthen data management. The health staff responsible for collecting entomological and epidemiological data should be given electronic devices like tablets or mobile phones. The field staff should enter surveillance data through these digital devices. For example, Kenya moved away from manual data reporting to electronic data reporting for its National Tuberculosis, Leprosy and Lung Disease Programme with an Android based application called TIBU. Florida's Department of Health puts out weekly and annual reports on surveillance. State health departments should also conduct impact analysis on vector control measures. NVBDCP and IDSP should make these studies publicly available to all the stake-holders including other State governments, the private sector and consumers.
  

Building a generalised and integrated communicable disease management system is laying infrastructure. It can be used for tackling different problems from year to year. Our objective should be to lay this general infrastructure, and not narrowly run campaigns targeting one disease or another.

For an analogy, consider Aadhar. Aadhar is just an identity platform. However, it has been built on robust technology using sound processes. In itself, Aadhar does not do much. However, Aadhar can act as a backbone for multiple initiatives ranging from financial inclusion, rationalising subsidies, targeting delivery of public services, national security, preventing corruption and leakage, etc. It constitutes a general purpose infrastructure which builds a platform on which many specific public services can run.

In similar fashion, a well designed communicable disease management platform which leverages technology can be used to deal with kala-azar and filariasis this year, but can be used for malaria, chikungunya and dengue the next year. The same surveillance, monitoring and data dissemination systems will work for multiple diseases. So far, the government has integrated the disease surveillance programme, i.e. brought multiple programmes under one umbrella but it has not re-imagined the way it should be carried out.

References

The case for Universal Healthcare is weak by Jeffrey S. Hammer, July 2015, Ajay Shah's blog

The lost hope of elimination of Kala Azar (visceral leishmaniasis) by 2010 and cyclic occurrence of its outbreak in India, blame falls on vector control practices or co-infection with human immunodeficiency virus or therapeutic modalities by Muniaraj Maylisamy, 2014, Tropical Parasitology

Epidemiological features of pneumonic plague outbreak in Himachal Pradesh, India by Joshi K et al., May 2009, Transactions of the Royal Society of Tropical Medicine & Hygiene

Quick control of bubonic plague outbreak in Uttar Kashi, India by Mittal V et al., December 2004, The Journal of Communicable Diseases

Report of the Working Group on Disease Burden for the 12th Five Year Plan by Planning Commission, Govt. of India, May 2011

Adult and child malaria mortality in India: a nationally representative mortality survey by Dhingra Neeraj et al., October 2010, The Lancet

A high malaria prevalence identified by PCR among patients with acute undifferentiated fever in India by Haanshuus CG et al., July 2016, PLOS ONE

Economic and Disease Burden of Dengue Illness in India by Shepard Donald S. et al., December 2014, The American Journal of Tropical Medicine and Hygiene

Need for an efficient adult trap for the surveillance of dengue vectors by Sivagnaname N. and Gunasekaran K., Indian Journal of Medical Research, November 2012

Handbook for integrated vector management by World Health Organization, 2012

Smriti Sharma and Shubho Roy are researchers at the National Institute of Public Finance and Policy, New Delhi.