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Boletín chileno de parasitología

versión impresa ISSN 0365-9402

Bol. chil. parasitol. v.55 n.1-2 Santiago ene. 2000

http://dx.doi.org/10.4067/S0365-94022000000100003 

Evaluation of the losses produced by hydatidosis and cost/benefit analysis of different strategic interventions of control in the Province of
Rio Negro, Argentina

Edmundo Larrieu1, Carlos Mercapide1, Mario Del Carpio1, Juan Carlos Salvitti1, María Teresa Costa1, Susana Romeo1, Gustavo Cantoni1, Alicia Perez1, Amar Thakur1*

1) Consejo Provincial Salud Pública de Río Negro, Laprida 240 (8500) Viedma, Argentina.

2) Instituto Panamericano Protección Alimentos y Zoonosis (OPS-OMS)

Resumen

Evaluación de las pérdidas producidas por la hidatidosis y análisis del costo/beneficio de
diferentes intervenciones estratégicas de control en la Provincia de Río Negro, Argentina.

Los programas de control de la hidatidosis requieren de la elaboración de ecuaciones costo/beneficio para la justificación técnica del mantenimiento de su fuente de financiamiento.

Así, el objetivo del presente trabajo es analizar los costos para los servicios de salud de la Provincia de Río Negro, Argentina, la atención médica de los casos económicamente alternativas futuras en las estrategias de control. Para ello se obtuvo información de casos humanos atendidos en tres hospitales, tratados con métodos quirúrgicos convencionales, con quimioterapia y con PAIR (punción, aspiración, inyección y reaspiración), procediéndose a valorizar las prácticas médicas efectuadas. Se estimaron asimismo costos del programa de control basado en la desparasitación de perros y de programas alternativos basados en diagnóstico masivo en personas mediante ecografía y serología, y tratamientos no convencionales.

Se estimmó un costo de tratamiento de US$ 4.511 por paciente, US$ 5.936 en cirugía convencional, US$ 1988 en PAIR y US$ 1.350 en quimioterapia con albendazol. Los costos globales de atención médica para 1997 fueron estimados en US$ 293.215, resultando un 77% inferiores a 1980.

Se estimaron los costos operativos del programa tradicional de control en US$ 440000 y uno alternativo basado en diagnóstico y tratamiento en US$ 260.218.

Se analizan relaciones costo/beneficio para cada una de las estrategias planteadas.

Key words (Palabras clave): hydatidosis (hidatidosis); cost (costo); control (control); treatment (tratamiento)

INTRODUCTION

In almost all the endemic areas of South America the prevalence Echinococcus granulosus infection in dogs varies from 15% to 75% and of hydatid cysts in sheep from 35% to 50%. There is also high prevalence of infection in cattle, goats, and pigs (Larrieu, 1991).

With regard to man in South America more than 2,000 new human cases are operated annually, 464 in Argentina (1.4 x 100,000 inhabitants), 367 in Uruguay (12.4 x 100,000), 573 in Chile (3.4 x 100,000), and 244 in Peru (2.4 x 100,000) (Ruiz, et al., 1994)

Howewer, the real hydatid cyst carrier rates can be very superior in some endemic areas: 2050 x 100000 in the south of Argentina, 5800 x 100000 in the south of Brazil, estimated on the basis of seroeactivity to double diffusion arc 5 (DD5) or of 6000 x 100000 to 14900 x 100000 in indigenous reserves and/ in rural areas of Neuquen, Chubut and Rio Negro (Argentina) determined on the basis of ultrasonographic (US) surveys, which is considered to be the most sensitive instrument to determine the prevalence of hydatidosis in a community (Frider et al., 1986, 1988)

This situation has motivated the implementation of several programs for hydatidosis control, financed by the Health Service Department (e.g. Argentina) or the Agricuture Sector (e.g.- Chile).

These programs require const/benefit analysis for the justification of its funding. These analysis are especially important in hydatidosis considering the long time requirest to reach permanent reductions in parasitic transmission.

In the present work the costs for medical care of human hydatidosis incurred by the Health Services of the Province of Rio Negro (Argentina) are analyzed. In addition, the economic impact generated by the hydatid disease control program carried out during the period 1980/1997 is also analyzed. Taking into consideration these costs, different alternatives of investment in future control strategies are evaluated.

MATERIAL AND METHODS

Estimate of costs of treatment of human hydatidosis

Detailed information on human hydatid cases were obtained from hospitals of San Carlos de Bariloche (Complexity VI), Viedma (Complexity VI), and Ing. Jacobacci (Complexity IV) of the Province of Rio Negro. The first two hospitals carry out conventional surgical treatments. while the third does unconventional treatments. through chemotherapy with albendazole or PAIR (puncture-aspiration-injection-reaspiracion).

For the estimate of costs of treatment, five hydatidosis patients were selected from each hospital in 1997. The cost of treatment was calcultated from the clinical histories and included all the event linked to consultation, derivation, hospitalization, diagnosis and treatment.

The assessment of the medical practices was done on the basis of the costs defined for public hospitals by Resolution 432 of the Ministry of Health and Social Action of Argentina

The chemotherapeutic treatment cost was established on the basis of the drug prices to the public and the cost of hospital service given to the patient.

The information on the number of total cases of human hydatidosis ocurred in the Province of Rio Negro was obtained from the database existing in its Central Health Service in the period 1980/1997.

Estimate of costs of hydatid control programs:

The information was obtained from the operational costs of the program for hydatidosis control of the Province of Rio Negro, Argentina, based on 8 praziquantel treatments per year of 12,000 rural dogs (Larrieu et al., 1994).

In addition, the expenses were based on the early diagnosis with US and serology, and treatment of the patients with nontraditional methods (albendazole and PAIR) were also estimated. To calculate this price-list in pharmacies, drugstore and suppliers of hospital inputs are used.

By the number of cases estimate to treat was considered: 10,000 children of 7-13 years old, 200 asymptomatic liver carriers detectable by US, 18 asymptomatic lung carriers detected immunologically, in asymptomatic belonging to age grop 7 to 13 years 2% positivity of the US (Frider et al, 1988), ELISA with 57% of sensitivity (Coltorti, 1986; Larrieu et al., 1994). The expectation linked to the natural history of the disease makes it possible to foresee that 100 of the asymptomatic liver cases will be kept in host/parasite equilibrium receiving medical service only after detection with US (Frider et al., 1999). Theoretically 118 diagnosed cases could receive treatment with albendazol and 47 (40%) of them could be treated with PAIR by eventual failure of the chemotherapeutic treatment.

RESULTS

Estimate of costs of treatment o human hydatidosis

The number of cases evaluated were 15 patients, of which 11 had liver cysts and 4 lung cysts (relation H/P 2.75/1). One of the patients with a liver cyst also had a kidney cyst.

In average the cost of medical care was US$ 4,511 (165-16,490). For conventional surgical treatment the average costs were US$ 5,936 (1,730-16,490) in one hospital and US$ 4,595 (2,225-9,035) in the other hospital. For the treatment with PAIR the average costs were US$ 1,998 (1,165, 3545), while for chemotherapeutic treatment US$ 1,350. (Table I).

TABLA I

Costs of medical care, according to hospital
and type of treatment, Rio Negro, Argentina., 1997.

 
Days hospitalization
Cost (US$)
 
by patient
per patient

Conventional treatment 1
20 (3/56)
5,936
Conventional treatment 2
18 (7/40)
4,596
PAIR Treatment
6 (3/15)
1,998
Chemotherapeutic treatment
2 (0/3)
1,350

 

The average time of hospitalization was of 20 days (range 3-56) in the fist hospital with conventional surgical treatment, 18 (range 7-40) in the second hospital, 6 (range 3-15) for PAIR and 2 (range 0-3) for chemotherapy.

In relation to the annual number of cases treated, it was estimated for 1997 overall costs of medical care by US$ 293,215.

A retrospective estimate on costs of medical care was established on the basis of average of days of hospitalization by patient in 1980 (31 days) and the number of cases treated in this year (200). The resulting figures were US$ 6,565 per patient and an overall cost of medical care of US$ 1,313,000.

The reduction of costs comparing 1980 with 1997 is of 31,3% per patient and 77% of costs of overall treatment (Table II).

TABLA II

Financial advantages obtained in health by
activities of the hydatidosis control program, Rio
Negro, Argentina, 1980/1997.

 
1980
1997
Reduction
 
 
 
(%)

New cases
200
65
67.5
Days by patient
31
16
48.4
Cost per patient
US$ 6565
US$ 4511
31.3
Cost per year
US$ 1,313,000
US$ 293,215
77.7

 

Estimate of costs of control programs and cost/benefit relations:

With regard to operational costs of the program for control, for 1980 it was of US$ 52.9 per dog/per year while in 1997 the reduction was of US$ 37 per dog/ per year, because of the lower costs of the drugs utilized for the canine disparasitization (praziquantel). For the control program of the Province of Rio Negro, with 12000 dogs under program in an area of 200,000 km2, it implies current annual operational costs of US$ 440,000 (Table III).

TABLA III

Operational costs program of hydatidosis control, in US$,
by dog and year. Rio Negro, Argentina, 1997.

Input
Cost per dog
Operational cost
 
and per year
12000 dogs

Praziquantel x 50 mg
1.7
20,400
Household distribution
of drug
26
312,000
Surveillance with
arecoline
7.3
87,600
Health education
2
24,000

Total
37
440,000

 

This investment made possible to reduce the canine echinococcosis prevalence from 41.5% in 1980 to 4.2% in 1986 (Odd ratio = 0.06 X2 of trend = 157 for the period 1980/1986), resulting in 1997 of 2.3% (Odd ratio = 0.47, X2 of trend = 41 for the period 1992/1997).

For the estimate of the cost/benefit relationship, a linear evolution both of the spenditures on medical care of patients with hydatidosis and the operational costs of the control program for the period 1980/97 was considered (Table IV).

TABLA IV

Operational costs of program of early massive
diagnosis of human hydatidosis, per 100
determinations and per year. Rio Negro,
Argentina, 1997.

 
Inmunological surve
Ecographical
Integrated
 
(ELISA)
Survey
Survey
 
 
 
 
Materials and
drugs
18.6
1.5
20.1
 
 
 
 
Mobility
50
150
150
 
 
 
 
Total
68.6
151.5
170.1

*In US$
 
 
 

 

Thus the saving in costs of medical care reaches to US$ 10,112,000 with an investment of US$ 9,688,000, if a stable trend was considered in the costs of medical care in the absence of control program, the profit of its implementation would reach to US$ 12,412,000.

The costs of complementary models to the program for control were estimated in US$ 17,010 for the evaluation of 100% of the infant poputation from 7 to 13 years with an estimated possibility of diagnosis of 93.5% of the existing asymptomatic carriers and US$ 243,208 for the treatment of 100% of the cases diagnosed with unconventional treatmnets (Table V)

TABLA V

Comparative costs of different strategies of
hydatidosis control, Rio Negro, 1997

Strategies Cost per year
  (US$ dollars) 
   
Systematic disparasitization,
12,000 rural
440,000
dogs, praziquantel 8 dos/year.  
   
Serological ultrasonographic
surey of 10,000 children
from 6 to 13 years old
17,070
   
Treatment of positive cases 243,208

Total integrated health program 700,278

 

In such a way, a massive program for diagnosis and treatment in people would imply an annual contribution of US$ 260,218, that is 39% less than a traditional program based on the systematic canine disparasitization.

DISCUSSION

The utilization of the analyses of cost/benefit and o of cost effect is a useful instrument in the decision-making process and has as a purpose to select the actions according to priorities utilizing an economic criterion that compares the costs with the resulting profits.

It is calculated that every year in countries of Latin America, in the slaughterhouses some 2 million viscera of cattle and 3.5 million viscera of sheep are destroyed because of the hydatidosis, which presupposes strong, economic losses. However, the association of the hydatid cysts with other parasitic diseases as Fasciola hepatica, does not allow to determine with precision the losses effectively generated by hydatidosis.

In addition, the eventual utilization of the infected viscera destinated for flour preparation or other industrial uses can rule out this type of losses in economic terms or to modify the cost/benefit relationship when the justification for the implementation of control measures is done talking into account this parameter.

It is considered that the presence of hydatid cysts in sheep or cattle is also the cause of economic losses due to lesser production of wool, meat or milk. However, this concept has not been demonstrated validly (Battelli, 1997).

An approximation to this estimate was done by the Livestock and Agricultural Service of Chile in the XII Region. The weight of lambs, adult sheep and total ovine population for the periods 1969/1978 (without program of control) and 1979/1988 (with program of control), was compared, in the absence of climatic variations or pressure of grazing, where it was found that as effect of the hydatid control program, an increase of 2.8% in the weigth of the lambs (p. 0.05), 5.6% in adult sheep (p < 0.01) and 4.3% in total ovine population (p < 0.01) (Jería et al., 1992).

Reports linked to lower milk production prepared in Italy are still under preparation, is under observation and difficult to verify (Attanasio and Palmas 1972).

Taking into consideration all these aspects, it is extemely difficult to calcultate cost/benefit equations in control of hydatidosis bases on generated losses to the livestock activity.

With regard to the expenditures of the health sector, the costs of the conventional medical treatments for hydatidosis have been reported as US$ 2,197 in Uruguay and US$ 1,300 in Peru (Ruiz, 1994).

The costs of conventional medical treatment in the Province of Rio Negro, Argentina, found in the present work reached to US$ 4,598-5,936) per patient.

To the costs produced by the treatment of human hydatidosis, in addition, there should be computed the loss of working days, the loss of production generated by the case-fatality (potential years of missing life), and the loss of agricultural and livestock production by abandonment of the field when marginal producers, habitual in the Southern Argentina, should be transferred to distant surgical centers for large number of days.

These costs have not been mentioned in the present work and are not considered for the cost/benefit estimations.

In the Province of Rio Negro, Argentina, the result obtained as regards to the situation of human hydatidosis by the systematic canine disparasitization and the introduction of new diagnostic technologies and medical treatment reduced the time of hospitalization of 31 days in 1980 to 18 days in 1997 and the number of cases from 200 to 65 in the same period of time.

The cost/benefit relationship was, thus, favorable.

An aspect to evaluate, however, is the persistence of levels of transmission of echinococcosis of dogs to man. Thus, the reduction in the prevalence of canine echinococcosis caused less detection of infected dogs with the use of available technology and the current financial support, do not result in the elimination of the agent from the environment, and the higt costs of the household distribution of the drug, all these factor, thus, are the principal drawback for the achievement of this objective.

This situation presupposes the maintenance of the financing of activities of control by prolonged or even boundless time, with no possibility of including modern technology (for example availability of immunization in the intermediate host) or by increasing the financing (for example in order to improve the coverage of systematic canine disparasitization in attack phase in such a way to take the parasite toward its effective extinction).

The use of diagnostic possibilities currently available and the new therapeutic options in the treatment of human hydatidosis permit, now, to do new considerations of cost/benefit analysis.

The advantages and limitations of the US and the serology in the early diagnosis of human hydatidosis in asymptomatic patients of endemic areas have been sufficiently evaluated in regard to sensitivity, specificity, and predictive value (Frider et al., 1985, 1986; Larrieu et al., 1989; Gharby, 1992; Perdomo et al., 1988, 1997 Caremani et al., 1996).

With regard to operational costs, the serological diagnosis has the advantage of not requiring mobilization of professional human resources to the rural environment, since the samples can be obtained by local personnel, such as teachers and community agents (Guarnera et al, 1993). In the case of the US, its greater operational cost is linked to the need of transferring professional personnel to the rural environment, although it has been demonstrated the technical feasibiliy to operate this with local non- professional personnel (Saint Martín et al., 1988). Its high sensitivity, however, convert in into the technique of choice.

The chemotherapeutic treatment with albendazole and puncture-aspiration-injection-reaspiration of cysts (PAIR), have made possible strong reductions in the time of hospitalization, in the general costs of care and in the reduction of the social costs by lower loss of working days and the derivation of rural inhabitant to centers, of surgical complexity. Its effectiveness in the treatment of human hydatidosis is already a confirmed fact (Gil Grande et al., 1993; WHO Informal working group on Echinococcosis, 1996; Horton, 1997; Filice and Brunetti, 1997).

These therapeutic options are promising if asymptomatic patient concerned is diagnosed precociously (Salvitti et al, 1997; Pelaez et al., 1997, 1999), permitting even the option to limit the medical action to the US monitoring of the carrier.

Knowledge of natural history of the disease makes possible to predict that in approximately 66% of asymptomatic carriers of liver cysts the size will keep stable and without generating symptomatology throughout life of the carrier (Frider et al., 1999). On the other hand, the cysts of liver localization constitute approximately 85% of the existing cysts in asymptomatic carriers (Frider et al., 1988; Schenone, 1989).

Thus, the possibility of developing, prevention strategies based on the implementation of massive programs for early diagnosis through US and serology, with later monitoring or unconventional early treatment can be currently evaluated.

The operational costs of this strategy are proportionately low with regard to the massive programs for canine disparasitization and can be evaluated as alternative and/or complement to the traditional programs for systematic disparasitization of dogs utilized up to the present in order to limit or eliminate the health impairment produced by this disease, and with successful results in insular systems (Cyprus, Tasmania, New Zealand) with complete elimination of the agent from the environment; but with more limited success upon being developed in continental areas (Argentina, Chile, Brazil, Peru, Uruguay) where the possibility of definitive elimination of the parasite is considerably lower.

It is of course clear that the lower costs of the program for diagnosis and treatment of the human population and of systematic canine disparasitization is applicable exclusively to the Province of Rio Negro after almost 20 years of disparasitization of rural dogs, and that, the suppression of this activity could generate in few years an increase in the number of cases capable of inverting the terms of the equation.

However, the health care systems of countries where hydatidosis is endemic, now have technological possibilities economically feasible to implement, in order to prevent and resolve the health problems generated to the people by this disease.

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