The Economic Burden of Cutaneous Leishmaniasis and Hiv Co-Infection in Brazil and Potential

THE ECONOMIC BURDEN OF CUTANEOUS LEISHMANIASIS AND HIV CO-INFECTION IN BRAZIL AND POTENTIAL IMPACT OF NEW DRUG THERAPIES

by

Stephanie Kruchten

B.A., Johns Hopkins University, 2011

Submitted to the Graduate Faculty of

the Epidemiology Department

Graduate School of Public Health in partial fulfillment

of the requirements for the degree of

Master of Public Health

University of Pittsburgh

2013

UNIVERSITY OF PITTSBURGH

GRADUATE SCHOOL OF PUBLIC HEALTH

This essay is submitted

by

Stephanie D. Kruchten

on

April 15, 2013

and approved by

Essay Advisor:

Nancy W. Glynn, PhD ______

Research Assistant Professor

Department of Epidemiology

Graduate School of Public Health

University of Pittsburgh

Essay Reader:

Bruce Y. Lee, MD, MBA ______

Associate Professor

Departments of Medicine, Epidemiology, and Biomedical Informatics

School of Medicine and Graduate School of Public Health

University of Pittsburgh

Essay Reader:

Linda Rose Frank, PhD, MSN, ACRN, FAAN______

Associate Professor of Public Health, Medicine, and Nursing

Department of Infectious Diseases and Microbiology

Graduate School of Public Health

University of Pittsburgh

Copyright © by Stephanie D. Kruchten

2013

Nancy W. Glynn, PhD

THE ECONOMIC BURDEN OF CUTANEOUS LEISHMANIASIS AND HIV CO-INFECTION IN BRAZIL AND POTENTIAL IMPACT OF NEW DRUG THERAPIES

Stephanie D. Kruchten, MPH

University of Pittsburgh, 2013

ABSTRACT

Co-infection of HIV and cutaneous leishmaniasis (CL), an opportunistic disease among those with compromised immune systems, has emerged as an important public health concern in Brazil, due to an increase in the incidence of both infections. Pentavalent antimonials, amphotericin B, and miltefosine are all used for CL treatment among HIV positive individuals; however the utilized dosages vary between medical professionals and no designated treatment regimen for co-infected individuals exists. Due to the limited information available on the co-infection of these diseases, two Markov decision analytic computer models were created to evaluate the additional cost of CL in those co-infected with HIV when using currently available treatments and when a theoretical new treatment is used to treat CL/HIV co-infection. Results indicated that the least expensive lifetime cost per co-infection case is 14.4 times greater ($1,345) than the most expensive single infection case ($93). When comparing the current treatment options to the different scenarios of a theoretical new treatment, it is clear that focusing on new drug development effective for treating CL patients co-infected with HIV would provide considerable benefits. If CL incidence and the likelihood of CL/HIV co-infection continue to rise in Brazil, the total economic burden of CL due to co-infection (currently estimated between $0.2-6.8 million) will likely continue to increase, indicating a further need for research and development efforts for a safe effective drug to treat CL among those co-infected with HIV.

TABLE OF CONTENTS

1.0introduction

1.1CUTANEOUS LEISHMANIASIS

1.2HIV in brazil

1.3brazil and co-infection

2.0Methods

2.1model structure: co-infection model

2.2model structure: new treatment model

2.3Model Parameters

2.4Sensitivity analyses

3.0Results

3.1Co-Infection model

3.2new treatment model

4.0Discussion

5.0limitations

6.0public health significance

6.1public health policy

6.2health care system

6.3health care practitioners

7.0Conclusion

BIBLIOGRAPHY

List of tables

Table 1: Model Inputs

Table 2: Cost per Co-Infection Case

Table 3: Cost per Co-Infection Case with New Treatment

List of figures

Figure 1: Transitional Health States

Figure 2: Cutaneous Leishmaniasis Model Structure

Figure 3: HIV/CL Co-Infection Model Structure

Figure 4: New Treatment Co-Infection Model Structure

Figure 5: Net Present Value of Countrywide CL-Related Costs due to CL/HIV Co-Infection vs. Percent of Cases with CL/HIV Co-Infection

Figure 6: Net Present Value of Countrywide CL-Related Costs Due to CL/HIV Co-Infection Utilizing a New Treatment vs. Percent of Cases with CL/HIV Co-Infection

1

1.0 introduction

Leishmaniasis is a parasitic neglected tropical disease seen in the tropics, subtropics, and parts of southern Europe. The infection is caused by the Leishmania parasite spread through the bite of female phlebotomine sand flies and can also spread from person to person through open wounds [1]. There are two main forms of Leishmania infection: visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL) with a worldwide prevalence of 12 million cases [2]. Globally, the disease is underestimated and is on the rise in several countries [3]. If left untreated, VL can be deadly and both VL and CL are considered to be an opportunistic disease for those with HIV [4]. The World Health Organization (WHO) considers the leishmaniases a severe parasitic disease, and many groups including the World Health Assembly advocate on behalf of control and elimination of the disease [3].

1.1 CUTANEOUS LEISHMANIASIS

Cutaneous leishmaniasis is a significant problem in many parts of the developing world, affecting nearly 90 countries, and is separated into two categories: New World (the Americas) and Old World (Europe, Asia, Africa) [5, 6]. It is estimated that there are 1 – 1.5 million new cases of CL per year worldwide but due to under reporting, the actual number of new cases may be much higher [7]. There are approximately 62,000 new cases that occur in South and Central America yearly [8]. While 26,008 cases of CL have been reported per year between 2003 and 2007 in Brazil, it is believed the actual annual incidence of CL is between 72,800 and 119,600 due to under reporting [9]. CL presents itself as a papule that develops 1 to 12 weeks after initial infection [3]. The papule grows into an ulcer between 0.5 and 3 cm in diameter and typically those infected have more than one lesion [3]. Most lesions caused by CL heal spontaneously within a few months but leave scars in their place [6]. It has been noted that there is a seasonality associated with the disease, with increasing incidence during warmer months between May and September [10, 11]. Topical, systemic, and non-pharmacological treatments have all been used for CL but intralesional injections of pentavalent antimonials are the most common form of first line treatment [12].

After having a CL episode, a patient can develop mucocutaneous leishmaniasis (MCL) and diffuse cutaneous leishmaniasis (DCL) years after the initial lesion has healed. MCL is considered to be a chronic form of CL that is mainly seen in South America [13]. The disease spreads into the mucous membranes of the nose, mouth, and throat and can cause large amounts of damage and disfiguration [3]. Some risk factors for the development of MCL are gender, age, disease length, nutrition, genetics, skin lesion location, presence of other diseases, and no previous treatment for CL [14, 15]. The mucocutaneous form never self-heals, can be incredibly difficult to treat, causes disfiguration, and in some cases can even cause death [6, 16]. DCL is a form of CL that causes non-ulcerative nodules that are positive for parasites and have disseminated throughout the entirety of the body [6, 17]. It is considered a rare form of the disease with very few cases diagnosed each year in Brazil [18].

The three main species of Leishmania that affect Brazil’s population, L. braziliensis, L. amazonensis, and L. guyanensis are each associated with varying risks of severe disease outcomes [19]. Nearly 60% of CL cases in Brazil are due to L. braziliensis and 1-3% of those cases will develop MCL [19, 20]. Approximately 20% of CL cases are due to L. amazonensis and 30% of those cases will develop DCL [19].

1.2 HIV in brazil

Although Brazil’s first case of HIV was thought to have occurred in the 1970s and the first known case of AIDS in the country was reported in 1980 in Sao Paulo [21]. There has been an increased incidence of HIV throughout Brazil over the past few decades specifically among women, uneducated, and poor populations, due in part to the decrease in the mortality rate associated with HIV and AIDS in Brazil [21]. Brazil started implementing HIV education programs and campaigns to educate the nation on HIV and ways to protect yourself against infection [22]. These programs targeted the at-risk populations such as injection drug users, men who have sex with men, and sex workers [22]. In response to the high cost of AIDS treatment in the 1990s (exceeding $10,000 USD per patient annually), Brazil began to develop highly active antiretroviral therapy (HAART) and has provided access to free HIV/AIDS care since 1996 [22]. In 1996, the Brazilian Congress enacted a law that stated all individuals with AIDS would be granted free treatment [23]. Brazil produces non-patented versions of generic antiretroviral therapies as well as negotiates lower prices on patented therapies to lower the countrywide cost for treating HIV/AIDS [24]. Brazil is one of two countries that have sustained nationwide access to drug therapies for HIV [23]. By 2004, Brazil was able to reduce AIDS mortality by 50% and hospitalizations due to AIDS decreased by 80% since 1996 [23]. In 2009, there were approximately 660,000 people living with HIV/AIDS and the number continues to rise, especially among the risk populations in Northeastern Brazil [22].

1.3 brazil and co-infection

Brazil has a population of over 193 million people [25]. HIV and CL are both significant health problems in Brazil. The incidence of HIV was documented as 12.3 per 100,000 people in 2001 and incidence of cutaneous leishmaniasis was noted as 23 per 100,000 people in 2004 resulting in over 1.1 million people with HIV and 8 out of 100,000 Brazilians dying from the disease [21, 26, 27]. The burden of these diseases has been further exacerbated by the increase in occurrence of co-infection. Since 1990, 31 countries have reported cases of leishmania and HIV co-infection [28]. The number of leishmania and HIV co-infection cases has increased more rapidly than the number of reported AIDS cases during the same period of time, indicating a need for further surveillance and monitoring [28].

By 2003, nearly 100 cases of leishmania HIV co-infection had been presented in formal literature [21]. All cases were followed up by the WHO’s global network for the surveillance of Leishmania/HIV co-infection and it was discovered that 63% of the co-infection cases were due to either CL or MCL with 37% attributable to VL [21]. Approximately 70% of all cases were present in people between the ages of 20 and 40 [21]. As the co-infection of the diseases is fairly new, the best treatment regimen is still debated as detailed accounts of treatment and outcomes for co-infection cases have been rarely documented, most being anecdotal [29]. Pentavalent antimonials, amphotericin B, and miltefosine have all been used to treat CL or MCL co-infection with HIV [29].

2.0 Methods

Two Markov decision analytic computer simulation models were constructed utilizing TreeAge Pro 2012 (TreeAge Software, Williamstown, MA) to quantify the additional burden of co-infection, effect of this additional burden on national estimates, and the potential benefits of new treatment development in Brazil. One model focused on comparing the single disease of CL to the co-infection between CL and HIV using the cost and probabilities of current treatment for CL (the Co-Infection Model). A second model was developed to determine the potential cost/economic benefit of a theoretical new treatment for CL was developed targeting those with the co-infection (the New Treatment Model). The New Treatment Model was utilized to illustrate the potential variations in drug developments while being economically beneficial and establish future targets for drug development. The age at which individuals entered the model was determined by a triangular distribution with a range between 1 and 62 and a mean of 37 where individuals would cycle until death. The inputs of both Markov decision trees can be seen in Table 1, separated by single infection, co-infection, or seen in both. All past and future costs were converted to 2013 US$ utilizing a discount rate of 3% [30].

Table 1: Model Inputs

2.1 model structure: co-infection model

The Co-Infection Model compares the single infection of cutaneous leishmaniasis with the co-infection of CL and HIV. Figure 1 illustrates the various ways individuals can transition between health states in the Co-Infection Model.

Figure 1: Transitional Health States

Individuals in the single disease path had the ability of transitioning between six mutually exclusive Markov states [41]:

• Uninfected: Healthy individuals, not infected with CL.
• Cutaneous Leishmaniasis: Individuals currently infected with CL that could only stay in this state for one year.
• Prior Infection: Individuals who have recovered from CL, MCL, or DCL. Individuals can stay in this state for a maximum of ten years or until they have died or contracted CL, MCL, or DCL.
• Mucocutaneous Leishmaniasis: Individuals currently infected with MCL, only contracted after an initial case of CL.
• Diffuse Cutaneous Leishmaniasis: Individuals currently infected with DCL, only contracted after an initial case of CL.
• Death: Individuals died and are unable to continue to cycle through the model.

All individuals are entered into the model as infected with CL. At the end of the year, they transition out of the CL state into either death or prior infection. While in prior infection, individuals have the probability of dying, contracting CL, MCL, or DCL, remaining in the prior infection state, or transitioning into the uninfected state after having been in the prior infection state for ten years. Individuals in the uninfected state can transition to death, CL, or remain as uninfected. The transitioning of MCL and DCL are similar; individuals can either transition into death, prior infection, or remain infected with either MCL or DCL. A more complete diagram of the transitions and model structure for the single CL infection can be seen in Figure 2. As depicted in Figure 2, individuals can be treated for their infection, be cured of infection, have side effects from treatment, or continue to be infected without medical assistance. In the diagram, ‘kidney’ refers to the renal toxicity occasionally seen when amphotericin treatment is used for MCL and DCL. All probabilities and costs have been listed in Table 1.

Figure 2: Cutaneous Leishmaniasis Model Structure

While these transition states hold true for a mono-infection case of leishmaniasis, the co-infection path has four mutually exclusive Markov states that those with HIV can transition between:

• Uninfected: Individuals do not suffer from CL but are still HIV positive.
• Cutaneous Leishmaniasis: Individuals with both CL and HIV. Unlike the single CL infection, individuals are not required to leave this state after one year.
• Mucocutaneous Leishmaniasis: Individuals with both CL and HIV. Unlike the singular CL case, individuals do not need a prior CL infection before contracting MCL.
• Death: Individuals died and are unable to continue to cycle through the model.

All individuals are sent into the model as infected with either CL or MCL. While in either the CL or MCL states, individuals can transition to the states of death, uninfected, or remain in either CL or MCL. Both states have similar transitions but with differing probabilities and costs associated with treatment, cure, and side effects (Table 1). Individuals in the uninfected health state can either transition to death, CL, MCL, or remain as uninfected. A more complete diagram of the transitions and model structure for the co-infection can be seen in Figure 3. Unlike individuals in the single infection branch, individuals in the co-infection branch have the probability of dying due to miltefosine treatment, although this probability is fairly small. Additionally, once a side effect has been recorded for an individual, they may not receive the same medication again. The side effects are labeled as Liver and Creatinine in the miltefosine treatment and Kidney for the amphotericin treatment. Liver refers to elevated liver enzymes and creatinine refers to elevated creatinine and BUN levels in the blood after taking miltefosine. As with the single infection for MCL and DCL, Kidney refers to renal toxicity after taking amphotericin.

Figure 3: HIV/CL Co-Infection Model Structure

2.2 model structure: new treatment model

The New Treatment Model compares the co-infection branch as depicted in the Co-Infection Model with a new Markov state that uses a theoretical new treatment for CL for those infected with HIV. The transitional health states of the new treatment are similar to those of the co-infection transitions depicted in Figure 1. There are four mutually exclusive Markov states that those with the new treatment can pass through, similar to those with the co-infection:

• Uninfected: Individuals do not suffer from CL but are still HIV positive.
• Cutaneous Leishmaniasis: Individuals with both CL and HIV. Unlike the single CL infection, individuals are not required to leave this state after one year.
• Mucocutaneous Leishmaniasis: Individuals with both CL and HIV. Unlike the singular CL case, individuals do not need a prior CL infection before contracting MCL.
• Death: Individuals died and are unable to continue to cycle through the model.

Again, individuals are entered into the model infected with either CL or MCL. While the transitions are the same, the treatments received have varied and thus so have the costs and probabilities. Those in the new treatment branch have received a theoretical new treatment aimed to reduce the effects of CL in those who are HIV positive. Figure 4 has a more complete model structure and transition states. Individuals in the New Treatment Model do not have associated hospital costs for treatment, as it is assumed the theoretical treatment would not require an extended stay. As in the Co-Infection Model, if individuals experienced side effects from treatment, they were not given the treatment again. However, unlike the Co-Infection Model, no other treatments were offered after the presentation of side effects.