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La lutte antivectorielle en France

 | 
Didier Fontenille
, 
Christophe Lagneau
, 
Sylvie Lecollinet
, 
et al.

Assessment of vector control

Economic assessment: France lags behind1

Texte intégral

  • 1 In this chapter, references to the CD-ROM concern question 8: “What economic approaches are used i (...)

1Various reports have often stressed that French public and veterinary health policies suffer from a serious deficiency in assessment, especially of the economic dimension. That is particularly true for vector control. The case of bluetongue disease in ovines is a symbolic example. At present it is almost impossible to assess quantitatively the losses linked to the epizootic disease, whether direct (deaths, weight loss, fall in milk production, fertility problems and abortions) or indirect (stemming from circulation or animal trading restrictions, confinement to farms of animals earmarked for export). For this reason, in March 2008, the Ministry of Agriculture and Fisheries set in place a national observatory devoted to ensuring a better follow-up and better assessment of the economic repercussions of bluetongue.

2As a prelude to the account that follows, it is important to point out that the notions of “economic assessment of vector-borne disease” and “assessment of vector control”, although closely linked, are not equivalent. The costs of vector control (or direct costs) represent part of the overall costs of the disease. Moreover, when assessment is made of the costs/advantages of vector control, it is important to be able to evaluate the “cost-effectiveness” of the expenditure committed in relation to those that would be required for other public health strategies. Economic analysis of vector control will inevitably therefore make reference to the economic burden imposed by the disease in question.

OBJECTIVES AND METHODS

3Both public and private decision-makers have the task of deciding the allocation of resources by definition limited to health actions considered as priority elements. How then are these priorities determined? The economic assessment of vector control aims precisely to provide them with a set of criteria so that they can base their decisions on the costs and consequences of the different possible options and finally compare these competing choices.

The purpose of economic assessment

4The purpose of economic assessment is to go beyond the straightforward “intuitive” assessment and to bring into evidence the competing strategies, on the one hand, and the influence of the choice of view point of the study, on the other. Strategies can be identified only by means of a systematic description of acts of prevention, treatment, types of organization and so on but, thus far the analyses done in France have not followed this approach. As for the second aspect, it appears that in France only the point of view of public operators is considered, rarely that of the company or other, which would probably lead to a different health strategy.

5Finally, economic assessment gives a conclusion in conformity with the principles of economic calculation: the “best” decision is decided on the basis of its opportunity cost and not on its cost purely in the accounting sense (the best decision has the lowest opportunity cost).

The methods of economic assessment

6The methods of economic assessment can be grouped into three categories, according to whether the consequences are measured in physical, monetary or subjective terms. Economic assessment of vector control generally consists in establishing for each health strategy a relation between costs and the consequences of this strategy. Cost-effectiveness analysis is probably the simplest to apply and hence the most used.

Cost-effectiveness analysis

7The most appropriate strategy is not necessarily the least costly but the one that produces the best effect for the smallest cost. For the different prospective control options, a common measure of effectiveness (number of years of life gained, number of cases avoided, and so on) must be associated to obtain a cost per unit of effect (for example X Euros per year of life gained) or, in an equivalent way, an effect per unit cost (for example, number of years of life gained per Euro spent). The cost-effectiveness analysis allows intra-national and international comparisons to be made if the mea-sure of effectiveness used is the same.

Cost-benefit analysis

8If the consequences of the different strategies considered are not identical or if more than one effect is expected for at least one strategy, a cost-effectiveness analysis would not be appropriate (see CD-ROM). The idea is then to incorporate the different criteria by referring to a common monetary denominator (criteria such as the number of years of life gained, cases of disease avoided and so on are converted into a monetary unit). Consequences and costs of the different strategies are thus expressed in one and the same (monetary) unit and either the cost/benefit ratios or the net benefits of implementing the strategies can be used. This approach can prove to be especially suitable for measuring the impact of unwanted side-effects of vector control and its acceptability for the community involved.

Cost-utility analysis

9This method expresses the effects of health strategies in terms of preferences for individuals or for society. It is assumed that the economic agents have preferences or reach certain levels of satisfaction or utility regarding the states of health that the various strategies can attain. That comes down to standardizing in non-monetary terms the different effects to which these strategies lead (see CD-ROM). This type of analysis can be particularly well adapted if qualitative effects such as pain or comfort associated with treatments are integrated into the preoccupations of the study.

Prerequisites for application of these methods

10The cost-advantage analyses described use measures of the costs and effects of health. Analysis of costs necessitates data on the costs of consumption of resources for medical treatment (medicines, travelling medical service, hospitalisation, equipment and so on) and vector control, but also on costs for the patient and his family. The measure of the efficacy of a strategy is established and measured as physical health effects or in monetary terms or as preferences.

ECONOMIC SITUATION AND VECTOR CONTROL

11Before envisaging an economic assessment of vector-borne diseases of vector control, certain characteristics that might influence the way of proceeding must be mentioned.

The externalities and the connected concept of public good

12The externalities and the connected concept of public good induce market deficiencies which highlight the importance of individual behaviour for the elaboration of vector control policies. An externality occurs when the activity of consumption or production of certain economic agents influences, positively or negatively, the consumption or production of other agents, without this influence being expressed through prices. In the case of vector control, this can be such factors as the individual use of treated mosquito nets to reduce malaria transmission, poor upkeep of a garden that encourages vector proliferation. The problem comes from the fact that the externalities are not taken into account by the individuals who generate them through their choices. Private benefits and costs are thus not aligned on social benefits and costs (see CD-ROM).

13The notion of public good (such as environment, education) can benefit everyone although certain agents cannot be excluded. One of the problems stems from the difficulty of prompting individuals to contribute to its production or its financing (“if I benefit from it anyway, why would I contribute to it?”). Examples of contributions to the public good related to vector control include epidemic surveillance, insecticide spraying, environmental management, or health education. The production of environmental type public goods (global public goods) depends on smaller individual contributions.

Asymmetries of information

14Asymmetries of information are also a decisive factor for vector control assessment. Typically, some agents (households, patients, stockbreeders) have less information at hand than others (health professionals, the State, local authorities) on the diverse aspects of such control. This information deficiency can lead households not to adopt sound preventive practices or leave animals unvaccinated.

Public intervention

15Public intervention is necessary in order to compensate for the three market deficiencies just mentioned, whether by provision of the vector control service directly by the State, or by delegation of part of the control effort to other agents. Such intervention can also materialize in the form of information and communication campaigns or as regulatory and/or legislative measures.

16For private agents, incentive schemes could be offered by the State, especially mechanisms that might encourage their fullest involvement in providing public good (as subsidies for buying mosquito nets for instance). In cases where certain aspects of vector control are delegated to other agents (public or private), this delegation of management can in turn generate situations of ineffectiveness (moral hazard) which necessitates the provision of other incentive schemes.

17From the assessor’s point of view, the interests of private agents (households, care providers, pest-control companies) must be taken into account in the assessment of control strategies to integrate explicitly the basic economic characteristics that are the externalities, the public good and moral risk. If just the interest of the public financer were taken into account, some effects of the control efforts would be overestimated because these are dependent on the behaviour of private agents.

International standards

18Most public studies in academic books and journals and by international organizations (WHO, World Bank) deal with anti-malaria control. Beyond that, economic assessments of vector control also concern dengue, Chagas disease, West Nile virus fever, chikungunya, Lyme disease and trypanosomiasis. Moreover, the studies most often look at countries with lower economic development and standard of living than French regions affected by these same diseases. The methodologies used and the number of lessons drawn from these studies can help improve the assessment of vector-borne diseases and of the systems deployed to control these diseases.

Macro- and microeconomic approaches

19The macro- and microeconomic approaches for measuring the cost of disease are complementary. The micro- method is based on econometric study of the GDP growth rate, using vector-borne disease-related health indicators (like morbidity) as explanatory factors as well as the usual variables (location, type of economic organization). The macro- method, however, is founded on the disease’s impact on the economic agents, both public and private: the individual effects noted are subsequently combined to obtain the overall effect (at regional level or for a whole country). The microeconomic approach helps grasp better the channels for transferring costs and strategies to households, businesses and public agents. It is more suit-able for examining an improvement of vector control strategies even though it cannot take accurate account of external effects.

Economic impact

20Vector-borne diseases have an undeniable economic impact, as all the academic literature on the question shows. Countries affected by this type of disease indeed experience much weaker growth than the others.

Main channels of disease effect transmission to the economy

21Humans hit by a vector-borne disease find their productivity weakened (owing to fatigue, absenteeism), and this creates a cost for the employer company. The productivity of a patient’s family can also fall (helping the patient). The disease could also affect the accumulation of human capital, particularly in children (cognitive faculties are reduced).

22The veterinary sector is subject to similar detrimental effects: animals in poor health, production losses, reproduction problems, but also depreciation in the value of wool or meat produced, fall in pulling power of oxen in areas under the risks from trypanosomes.

23Direct investment made in countries affected by such diseases is seen as less profitable than elsewhere. In the long term there is a risk that investments will be diverted from an affected country. In parallel, a fall in tourism can be observed, whereas that sector is sometimes vital for these countries (Reunion Island, Mauritius).

24Moreover, the presence of vector-borne diseases leads to a fall in trade exchanges and in individuals’ mobility between infected and non-infected areas. This point is crucial for the veterinary field. The countries where regulation-covered diseases are rife see their exports blocked, leading to substantial indirect losses and possible destabilization of animal production sectors.

Choice of the cost-advantage analysis method

25In international studies, the principal assessment method used to date for the economic impact of a vector-borne disease, and the most straightforward to apply, is cost-effectiveness analysis. However, it could be appropriate to turn towards cost-benefit analysis, especially for incorporating unwanted side-effects of vector control into the equation (environmental pollution for example).

Point of view adopted

26The point of view adopted in these analyses is usually that of society. The interests of all the economic agents are therefore taken into consideration. It is essential also to include the point of view of private agents, as they are not only affected by vector-borne diseases, but also represent an important link in the vector-control chain. Thus, certain strategies will be judged more “efficient” if only the point of view of the State were to be considered, whereas their real effectiveness can be questioned if they engender higher costs for the private agents. That can lead to conclusions being considerably qualified, or sometimes even reversed (see an example in Sri Lanka on CD-ROM).

Measurement of costs of disease and of vector control

27As has already been recalled, these two types of cost are closely interwoven. Expenditure linked to vector control will be considered as an investment aiming to reduce the costs associated with the economic burden of the disease. Expenses related to diseases include those linked to prevention, diagnosis and treatment.

28Generally, direct costs are distinguished from indirect costs. Direct costs concern interventions and medical care supported by the public sector and private agents. Indirect costs, in the veterinary sphere, include losses in productivity due to disease and the consequences for the various production sectors. In public health these indirect costs are estimated by the income lost owing to disease or death of livestock. Ideally, certain more intangible effects, difficult to evaluate, should be added, such as the cost of pain.

Standardized measurements of effectiveness

29Studies make increasing use of standardized measures of health effects, inspired by good practice guides on assessment issued by WHO or the World Bank. Among the classic measurements are: deaths averted (DA), or discounted life years gained (DLYG). However, the one currently most favoured is disability adjusted life years (DALY), proposed by the World Bank and WHO in 1993.

30This is a non-monetary composite index which gives a figure for the impact of mortality and morbidity caused by disease, on the basis of an aggregation of “quantities “of time, abilities or professional activities lost. Some investigations use the DALYs even as a measure of the economic impact if there are no relevant data on costs. One of their main advantages is to avoid the use of monetary values associated with human lives (potentially problematic from the ethical or moral point of view) and, through its standardization, to allow comparison with the DALYs for other diseases, countries or strategies.

31However, no study opts for an intermediate measurement of effectiveness (for example the Breteau-type of vector density index).

Period and area of study

32Studies favour covering a sufficiently long period to embrace endemic and epidemic phases, which gives the opportunity to incorporate the medium and long-term effects. In spatial terms, small study zones are more suitable for gathering accurate data on economic, epidemiological and entomological dimensions (allowing homogeneity).

Conclusion on cost-effectiveness analyses

33The studies published in the literature are based on the measurement of what is possible during field surveys rather than on trials and simulation exercises, which guarantees quite robust results. They generally bring into evidence the economic impact of vector control actions and their effectiveness (in relation to control of other diseases).

ASSESSMENT OF VECTOR CONTROL IN FRANCE

34In France and her territories economic assessment of vector-borne diseases is currently limited to a number of tentative elements.

Data collected

35The data collected is limited to the costs borne by public sector vector control operators (the State, local authorities), with variable accuracy depending on the département involved (see CD-ROM). Yet accounting only for costs gives the public decision-maker a highly incomplete picture. In any case, these costs represent only part of the total expenditure. Costs incurred by private agents should be incorporated (owing particularly to incentives aimed at these agents), which moreover must be considered differently according to whether the point of view of the public sector or that of the company is adopted. Furthermore, the calculation of costs does not explicitly show up any depreciation for investment in capital or updating, and therefore cannot take account of any possible spreading of costs over time.

36This leads to poor reliability, seeing that vector control is a process applied over the medium or long term.

Economic approach

37When an economic approach does exist, it is restricted to the calculation of some extremely heterogeneous costs. Nevertheless some analyses of the impact of vector-borne diseases can be gleaned, such as that of INSEE Reunion (2006 and 2007) concerning the chikungunya epidemic’s impact on the island’s economy. However, its results, especially the finding that the cri-sis had only a low impact on growth, must be put into proper perspective for methodological reasons. In metropolitan France, it was an assessment of the economic consequences of bluetongue outbreaks on the grazing sector which was conducted. But there again this analysis does not lead to any figure for the overall cost of the disease for that sector (for more details on these two studies, see CD-ROM).

Vector control management scenarios

38Scenarios for the management of vector control could be used as a basis for future assessment. The following three scenarios for organization of vector control have, for example, been devised for two départements? Guadeloupe and French Guiana: complete management of actions within the DSDS (Direction de la Santé et du Développement Social, or “Health and Social Development Department”); actions contracted out but risk assessment and verification of effectiveness of actions remaining with the DSDS; subcontracting of all aspects. However, they still suffer from a large number of inadequacies (see CD-ROM).

Economic analysis

39Economic analysis of the organization of vector control entails taking a position in the framework of an “agency relation” or “Principal-Agent” relation, considering the delegation of management as established by the law of 13 August 2004 (see the chapter “Legislative and regulatory framework for vector control”): the Principal (the State) delegates to an agent (the département council and the municipal council for certain tasks). Generally, an agency relation is characterized by a situation where there is double asymmetry of information, the agent having private information at hand that the Principal has not. In concrete terms, the département council or the municipality holds information (vector density, local health and hygiene situation) not available to the State. Moreover, the actions of the agent (the département council) taken in the context of its duties cannot be observed or verified by the Principal, the State here. Hence there is a risk of failings in behaviour of the agent, the possibility of conflicts of interest and so on (see CD-ROM).

40In short, the problem for the State is that it does not have the information authorities hold at local level. Further, it cannot base itself on the level of result to infer information exclusively held by the agents, or again their level of effort, because the result in health terms follows an unpredictable process that falls partly outside the actions of the agent (it depends for example on the demographic situation of the vectors, their possible resistance to operations against them, the degree of immunity of individuals, the local effectiveness of biocidal products and so on). In the absence of exactly defined objectives and of any follow-up and assessment indicator, it is therefore difficult for the State to indict a département council or a municipality for bad management of vector control or attribute blame for an epidemic outbreak.

41This situation of information deficit can lead to two types of inefficiency from the point of view of the State. The State’s vector control strategy can be poorly adapted to the real conditions at local level. Or the level of vector control effort put in by the département council or the municipality is insufficient or inappropriate for the level the State expects of them in order to achieve its objectives. A solution for the first type of inefficiency would be to involve the local authorities more closely in defining the strategies. The second could be resolved by inserting in the “contractual” relationship an incentive mechanism encouraging the département council or the municipality to invest stronger or better adapted effort to meet the State’s expectations.

42An acceptable proposal would be to consider the département council and the municipality no longer as simply agents following orders but as principals in their own right. The State, the département council and the municipalities would form a committee which would take decisions on vector control strategy and implementation by common accord. A GIP type of structure could serve as this forum for cooperation, even if it is not perfect (there are risks of dilution of responsibility). Whatever the case may be, the form of organization is crucial because it could generate not only quite high agency costs, but also malfunctions in the implementation of vector control.

RECOMMENDATIONS
■ The creation of a structure, group or network of experts capable of conducting or driving the economic assessment of vector-borne diseases and of control against these diseases.
Methods similar to those applied at international level should be adopted, for measuring both the costs and effectiveness, so that decision-makers can make comparisons with other uses of resources.
Reliable data are needed on effectiveness and costs. That requires the identification of indicators, the instigation of enquiries and data gathering campaigns that are harmonized from one local authority to another and also at State level. Also essential is an examination of entomological indicators in the perspective of cost-effectiveness assessment. Access to data must also be made easier to allow more scientific research to be done on this aspect.
Cost-effectiveness analysis must be used as a priority, at least to begin with, as it is the most straightforward type of analysis to apply. This approach can be extended quite simply to take into consideration more intangible aspects such as acceptability and unwanted side-effects. There is a prospect in the medium term for applying more sophisticated assessment methods (cost-benefit or cost-utility analyses).
The choice of the form of organization for vector control must be examined in detail so that problems linked to delegation or malfunction in implementation can be kept to a minimum. Local authorities should be involved more closely because they have better information at their disposal than the State, and their participation in the strategic decision-making process will give them stronger incentive to work more fully in conjunction both with each other and the State services.

Notes

1 In this chapter, references to the CD-ROM concern question 8: “What economic approaches are used in vector control?”.

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