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Epidemiology and Clinical Features of Hydatid Cyst in Northern Iran from 2005 to 2015
brief-report
Author(s):
Parisa ISLAMI PARKOOHI
1 ,
Marjan JAHANI
2 ,
Fatemeh HOSSEINZADEH
3 ,
Shokufeh TAGHIAN
2 ,
Forugh ROSTAMI
2 ,
Abdollah MOUSAVI
3 ,
Mohammad Sadegh REZAI
3
,
*
Publication date (Print):
Apr-Jun 2018
Journal:
Iranian Journal of Parasitology
Publisher:
Tehran University of Medical Sciences
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Abstract
Background:
Human hydatid disease imposes significant impacts on public health by producing substantial morbidity and mortality in involved communities. This study aimed to evaluate the epidemiology and clinical features of hydatid cyst in northern Iran as a breeding center for the infection.
Methods:
In this cross-sectional study, the hospital records of all hydatidosis-affected patients admitted in three teaching hospitals of Mazandaran Province between Mar 2005–2015 were reviewed. Hydatidosis-relevant demographic characteristics, clinical findings, and laboratory data were collected. The descriptive statistical analysis was performed by SPSS software.
Results:
Totally, 79 patients with the mean age of 42.00±23.82 yr were admitted with cystic echinococcosis (CE) diagnosis. Moreover, the highest and the lowest prevalence of CE cases were in age ranges of 50–59 (19.0%) and more than 80 (5.0%) yr, respectively. Male/female ratio was 0.88 (47.0% vs. 53.0%). Majority of the cases were urban residents (54.0%) and had no close contact with animals (58.0%). Nearly, two third of the patients (n=54), the affected organ was liver. The diameter of the cysts was variable from 2 to 15 cm. Most of the patients had a single hydatid cyst. Four patients were diagnosed as secondary hydatid cyst. Medical treatment with antiparasitic agents was done for 47 individuals and in 7 cases; it was the only treatment approach. Percutaneous puncture-aspiration-injection reinjection (PAIR) technique was applied for 6 cases. Sixty-six patients underwent radical surgery. No data was available on eosinophil count or serological tests.
Related collections
Most cited references26
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Worldwide epidemiology of liver hydatidosis including the Mediterranean area.
The worldwide incidence and prevalence of cystic echinococcosis have fallen dramatically over the past several decades. Nonetheless, infection with Echinococcus granulosus (E. granulosus) remains a major public health issue in several countries and regions, even in places where it was previously at low levels, as a result of a reduction of control programmes due to economic problems and lack of resources. Geographic distribution differs by country and region depending on the presence in that country of large numbers of nomadic or semi-nomadic sheep and goat flocks that represent the intermediate host of the parasite, and their close contact with the final host, the dog, which mostly provides the transmission of infection to humans. The greatest prevalence of cystic echinococcosis in human and animal hosts is found in countries of the temperate zones, including several parts of Eurasia (the Mediterranean regions, southern and central parts of Russia, central Asia, China), Australia, some parts of America (especially South America) and north and east Africa. Echinococcosis is currently considered an endemic zoonotic disease in the Mediterranean region. The most frequent strain associated with human cystic echinococcosis appears to be the common sheep strain (G1). This strain appears to be widely distributed in all continents. The purpose of this review is to examine the distribution of E. granulosus and the epidemiology of a re-emerging disease such as cystic echinococcosis.
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Hepatic echinococcosis: clinical and therapeutic aspects.
Echinococcosis or hydatid disease (HD) is a zoonosis caused by the larval stages of taeniid cestodes belonging to the genus Echinococcus. Hepatic echinococcosis is a life-threatening disease, mainly differentiated into alveolar and cystic forms, associated with Echinoccus multilocularis (E. multilocularis) and Echinococcus granulosus (E. granulosus) infection, respectively. Cystic echinococcosis (CE) has a worldwide distribution, while hepatic alveolar echinococcosis (AE) is endemic in the Northern hemisphere, including North America and several Asian and European countries, like France, Germany and Austria. E. granulosus young cysts are spherical, unilocular vesicles, consisting of an internal germinal layer and an outer acellular layer. Cyst expansion is associated with a host immune reaction and the subsequent development of a fibrous layer, called the pericyst; old cysts typically present internal septations and daughter cysts. E. multilocularis has a tumor-like, infiltrative behavior, which is responsible for tissue destruction and finally for liver failure. The liver is the main site of HD involvement, for both alveolar and cystic hydatidosis. HD is usually asymptomatic for a long period of time, because cyst growth is commonly slow; the most frequent symptoms are fatigue and abdominal pain. Patients may also present jaundice, hepatomegaly or anaphylaxis, due to cyst leakage or rupture. HD diagnosis is usually accomplished with the combined use of ultrasonography and immunodiagnosis; furthermore, the improvement of surgical techniques, the introduction of minimally invasive treatments [such as puncture, aspiration, injection, re-aspiration (PAIR)] and more effective drugs (such as benzoimidazoles) have deeply changed life expectancy and quality of life of patients with HD. The aim of this article is to provide an up-to-date review of biological, diagnostic, clinical and therapeutic aspects of hepatic echinococcosis.
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The Monetary Burden of Cystic Echinococcosis in Iran
Introduction Cystic echinococcosis (CE), a chronic disease caused by the larval form of the tapeworm Echinococcus granulosus, is one of the most important helminth-associated zoonoses globally [1], [2]. The parasite's domestic life cycle involves livestock and dogs as the primary intermediate and definitive hosts, respectively. Canids harboring adult E. granulosus worms excrete eggs into the environment, where intermediate hosts become infected through ingestion of the eggs. Humans can also act as aberrant intermediate hosts if they ingest infective parasite eggs either through contaminated food or directly from an infected canid. A cystic larval form (metacestode) gradually develops, most commonly in the liver or lungs. However, other organs can also be affected. Clinical signs typically develop as a result of this space-occupying lesion exerting pressure on surrounding tissues. Rupture of the cyst and spillage of the contents may cause anaphylactic shock and secondary CE. In many parts of the world, including Iran, surgery remains the treatment of choice for most individuals suffering from CE [2]. Cystic echinococcosis is a cosmopolitan zoonosis, with highly endemic areas especially prevalent in regions of South America, North Africa, China, and the Middle East [2]. Iran is an important endemic focus of CE where several species of intermediate host are commonly infected with E. granulosus [3]. High infection prevalences, with different strains of E. granulosus, have been reported in various domestic livestock including sheep (5.1%–74.4%), goats (2%–20%), cattle (3.5%–38.3%), buffalo (11.9%–70%), and camels (25.7%–59.3%) [4], [5], [6]. Between 5% and 45% of dogs is reported to be infected with E.granulosus in different provinces of Iran (reviewed in [7]). Human CE cases are also regularly reported from medical centers in different parts of the country and the incidence of CE is estimated 1.18-3 per 100,000 populations in different regions [7]. Recently, the World Health Organization (WHO) included CE in a subgroup of selected Neglected Tropical Diseases (NTDs) to be addressed within its 2008–2015 strategic plan for control of NTDs [8], [9]. The WHO recommends that the impact of zoonotic infections be assessed before implementation of any control measure [10], [11]. Costs associated with CE have been shown to have a great impact on affected individuals, their families, and the community as a whole [12], [13]. Monetary losses due to CE have been estimated for Uruguay [14], Wales [15], Jordan [16], Tunisia [17], Turkey [18], Spain [19], Peru [20] and for a highly endemic area of the Tibetan plateau [21], [22]. In addition, the non-monetary burden of CE has been assessed for a highly endemic region of China and globally utilizing the disability adjusted life year (DALY) [23]. Although CE is assumed to be a significant public health and economic problem in Iran, the extent of its socioeconomic impact is not fully understood. Economic losses due to CE in ruminants have been previously estimated in three provinces of Iran (Khuzestan, North Khorasan, and Ardabil) [24], [25], [26]. However, these studies were not concerned with human CE and used potentially biased methods to estimate livestock-related losses. Accurate assessment of the disease burden is crucial to raise awareness of decision-makers and to prioritize use of limited resources to provide timely preventive measures [27], [28]. The purpose of the present study is to estimate the monetary burden of CE in Iran using existing country-level data on human and animal CE. Materials and Methods Human epidemiological data Population data for Iran for 2010 were extrapolated from the 2006 population census, with 71.8% of the population living in urban areas [29]. Due to a lack of surveillance data, the number of CE patients, by age and gender, that underwent surgery between 2000 and 2009 in 34 referral hospitals in seven of the country's most populous provinces (representing 51.4% of the total population) was collected to determine average annual surgical incidence. In total, 5,993 CE surgeries were identified over this 10-year period. For the remaining 23 provinces, data from individual scientific reports were used when available [30], [31], [32], [33]. For those provinces with no data, information from neighboring provinces with similar socioeconomic status was applied. Based on these sources, an annual number of 1,295 CE surgeries was calculated. All CE recurrences with re-operations were regarded as new surgical cases. Approximately 80% of surgical CE cases in Iran are treated in public hospitals, with the remaining 20% treated in private hospitals. Only surgical cases of CE were included in this study due to a lack of data on cases that seek treatment, but that are treated medically. In order to estimate the number of undiagnosed or asymptomatic cases of CE in Iran, data on ultrasound prevalence of CE (1.2% and 0.2%) were used (Table 1) [34], [35]. Lengths of hospital stay and mortality rates were based on available literature (Table 1). 10.1371/journal.pntd.0001915.t001 Table 1 Human epidemiological parameters associated with CE in Iran. Category Value Unit Distribution Range Reference Population (2010) 74,733,230 Individuals Fixed - [29] Urban/Rural 71.8/28.2 Percent Fixed - [29] Average income per day-urban 23.48 US$ Fixed - [29] Average income per day-rural 14.09 US$ Fixed - [29] Annual surgical incidence of CE 1.27 Per 100,000 Uniform 0.80–1.73 See Methods Hepatic cysts 55.5 Percent Fixed - See Methods Pulmonary cysts 30.9 Percent Fixed - [25], [31], [33], [51], [52]* Hepatic and pulmonary involvement 4.1 Percent Fixed - See Methods Other organs 9.5 Percent Fixed - See Methods Undiagnosed cases of CE 0.85 Percent Uniform 0.2–1.5 [34], [35] Length of hospital stay 11.4 Days Uniform 7–15.8 [53], [54], [55] Mortality among surgical cases 2.5 Percent Uniform 1–5 [56], [57], [58] No of absentee days for recovery 18 Days Uniform 8–28 [53], [54] Age and sex distribution ¶ 947 Individuals Uniform 599–1295 See Methods Male patients 0–9 4.6 Percent - - 10–19 14.5 Percent - - 20–29 20.4 Percent - - 30–39 16.9 Percent - - 40–49 13.9 Percent - - 50–59 10.5 Percent - - 60–69 10.1 Percent - - 70–79 7.5 Percent - - 80+ 1.6 Percent - - Total 100 Percent - - Female patients 0–9 3.6 Percent - - 10–19 9.7 Percent - - 20–29 19.0 Percent - - 30–39 19.2 Percent - - 40–49 16.8 Percent - - 50–59 13.9 Percent - - 60–69 10.3 Percent - - 70–79 6.3 Percent - - 80+ 1.2 Percent - - Total 100 Percent - - ¶ Based on surgical incidence. Livestock epidemiological data The livestock species primarily involved in the domestic cycle of CE in Iran are sheep, goats, cattle, buffalo, and camels. Data for livestock populations and annual numbers of slaughtered animals were obtained from official government reports (Table 2) [29]. The low percentage of the total sheep and goat population slaughtered annually (12.8% and 8.5%, respectively) may reflect the practice of slaughtering outside of abattoirs. To account for home slaughtering, losses were also evaluated assuming that slaughter rates are twice what are reported at the abattoirs, assuming a mean of 1.25 offspring per ewe/doe per year. Milk, wool, and hide/skin production values were based on either Statistical Center of Iran (SCI) reports or United Nation's Food and Agriculture Organization (FAO) FAOSTAT data [29], [36]. Livestock prevalence data were obtained from abattoir-based studies available from the literature. Only studies where a researcher confirmed the presence of CE cysts were included because abattoir-reported cases are not considered reliable in Iran. Prevalence data obtained from 3 or more studies were combined for cattle, sheep, and goats using a meta-analysis for proportions in R statistical data analysis software, ver. 2.12.0 (META package version 1.6-1; by Guido Schwarzer) (Table 2) [37]. Due to the limited available data for buffalos, a meta-analysis could not be performed for this species. Therefore, the mean prevalence from two studies on CE in buffalo in Iran (12.4% and 11.9%) was used [5], [26]. 10.1371/journal.pntd.0001915.t002 Table 2 Epidemiological parameters and annual livestock production values for Iran. Category Value (CI) Unit Distribution Reference SHEEP Population 49,976,138 Animals Fixed [29] *No of slaughtered animals/year 6,446,354 Animals Fixed [29] Prevalence of CE at abattoir 23.5 (8–39) Percent Normal [5], [26], [59], [60], [61], [62], [63], [64], [65] Meat production 390,000 Tonne Fixed [36] Milk production 444,004 Tonne Fixed [29] Skin/hide production 64,800 Tonne Fixed [36] Wool production 52,455 Tonne Fixed [29] GOAT Population 22,333,547 Animals Fixed [29] *No of slaughtered animals/year 1,912,640 Animals Fixed [29] Prevalence of CE at abattoir 8 (5–11) Percent Normal [5], [26], [59], [60], [61], [62], [63], [64], [65] Meat production 106,000 Tonne Fixed [36] Milk production 270,157 Tonne Fixed [29] Skin/hide production 18,875 Tonne Fixed [36] Wool production 2,905 Tonne Fixed [29] CATTLE Population 7,088,984 Animals Fixed [29] No of slaughtered animals/year 1,432,270 Animals Fixed [29] Prevalence of CE at abattoir 20 (13–27) Percent Normal [5], [26], [59], [60], [61], [62], [63], [64], [65] Meat production 360,000 Tonne Fixed [36] Milk production 5,965,728 Tonne Fixed [29] Hide/leather production 47,700 Tonne Fixed [36] BUFFALO Population 191,438 Animals Fixed [29] No of slaughtered animals/year 30,926 Animals Fixed [29] Prevalence of CE at abattoir 12.5 Percent Fixed [5], [26] Meat production 14,900 Tonne Fixed [36] Milk production 245,000 Tonne Fixed [29] Hide/leather production 2,048 Tonne Fixed [36] CAMEL Population 151,932 Animals Fixed [29] No of slaughtered animals/year 45,127 Animals Fixed [29] Prevalence of CE at abattoir 32 (15–49) Percent Normal [66], [67], [68], [69], [70], [71] Meat production 1,680 Tonne Fixed [36] * Assuming government-reported slaughter rates for sheep and goats. Human economic data Costs associated with direct and indirect losses associated with human surgical CE were assessed. Direct costs included cost of surgery, hospital accommodation, diagnostic imaging, clinical laboratory and histopathology testing, and drug costs in both public and private hospitals. The Puncture Aspiration Injection Re-aspiration (PAIR) technique, which is widely used in other parts of the world, is rarely used in Iran. Therefore, the procedure was not costed in this study. Unit costs of services were obtained from official tariffs established by the Iranian Ministry of Health and Medical Education [38]. Service costs were calculated by multiplying the unit cost of an individual parameter by its frequency in the course of disease. Expert attending surgeons from Afzalipour Medical Center in Kerman, Iran were asked to estimate the frequency of common CE-associated procedures and services when these data were not available elsewhere. Indirect costs associated with human CE included lost wages due to work absenteeism during hospitalization and recovery, due to time off to stay with a child with CE, and due to CE-related mortality. Income data for urban and rural populations were obtained from official reports of the CBI. Gender specific wage data were not available for Iran or its neighboring countries. Therefore, based on studies conducted in other regions, it was assumed that women earn approximately 0.70 times as much as men [19]. Breakdown of wages by age was also not available for Iran. Therefore, it was assumed that this breakdown would also be similar to the findings from other studies [19]. Unemployment figures were based on SCI data. Productivity for females who do not work outside of the home was assumed to be equivalent to 30% of the daily income of an officially employed female of the same age group [15]. A 100% loss of daily wages or productivity was assumed for CE surgical patients for the period of hospitalization. However, no losses were evaluated for unemployed patients since government unemployment benefits, which are received by all members of society whether they work in the public or private sector, were assumed to remain unchanged during the treatment period. Since unemployment benefit coverage is most likely not complete, the cost estimation is probably underestimated, especially in rural populations. For CE patients under the age of 18 years, a 30% wage loss for a man 30–39 years of age was applied for the period of hospitalization. This was based on the assumption that a parent would need to devote a proportion of his or her time to caring for the child [17], [19]. It was assumed that premature mortality causes an annual income loss of between 1 and 364 days in any given year. Therefore, a uniform distribution was defined for the number of lost days due to CE-related deaths. In asymptomatic individuals, lost wages were calculated in terms of annual monetary income and a productivity loss of 0–5% for one year (Table 1). Livestock economic data Direct and indirect costs due to CE-associated losses in livestock species were evaluated. Direct costs associated with CE in livestock are due to the condemnation of livers and lungs during carcass inspections in abattoirs. A uniform distribution was applied to liver and lungs losses based on market prices across Iran (Table 3). It was assumed that the entire liver and/or lungs of infected cattle, sheep, goats, and buffalo would be condemned. The cost of infected camel livers, but not lungs, was included in the estimate because camel lungs are not traditionally consumed in Iran. 10.1371/journal.pntd.0001915.t003 Table 3 Value of livestock parameters (per Kg) used to estimate the monetary burden of CE in Iran. Category Value (US$) Distribution Range Reference SHEEP Live animal 2.86 Uniform 2.46–3.26 [29], [36] Liver 10.12 Uniform 8.67–11.56 [72] Lung 10.12 Uniform 8.67–11.56 [72] Milk 0.50 Fixed - [36] Hide/skin 1.64 Fixed - [73] Wool 0.59 Fixed - [29] GOAT Live animal 2.78 Uniform 2.40–3.16 [29], [36] Liver 10.12 Uniform 8.67–11.56 [72] Lung 10.12 Uniform 8.67–11.56 [72] Milk 0.48 Fixed - [36] Hide/skin 1.14 Uniform 0.63–1.64 [73] Wool 0.59 Fixed - [29] CATTLE Live animal 2.54 Uniform 2.26–2.81 [29], [36] Liver 8.67 Uniform 7.71–9.63 [72] Lung 0.27 Uniform 0.24–0.29 [72] Milk 0.38 Fixed - [36] Hide/leather 1.14 Uniform 0.63–1.64 [73] BUFFALO Live animal 2.54 Uniform 2.26–2.81 [29], [36] Liver 8.67 Uniform 7.71–9.63 [72] Lung 0.27 Uniform 0.24–0.29 [72] Milk 0.51 Fixed - [36] Hide/leather 1.14 Uniform 0.63–1.64 [73] CAMEL Live animal 1.21 Fixed - [36] Liver 8.67 Uniform 7.71–9.63 [72]* Milk 0.38 Fixed - [36]* • Assumed to be similar to that of cattle. Indirect losses due to decreased carcass weight, reduction in milk production, decreased wool production, decreased hide/skin value, and reproductive losses were estimated. Values of livestock parameters used to estimate economic losses associated with CE were assumed to be similar to those used in previous assessments of livestock-associated CE losses [16], [17], [19], [21]. Based on these values, a 2.5% decrease in milk production, 15% reduction in wool quality, 5.5% reduction in fecundity, 10% decrease in hide/skin production, and 6.25% reduction in carcass weight were utilized for this study. Farmers' investment was not taken into account in the presented cost estimates due to lack of data on this topic available from Iran or other countries in this region. Uncertainty and sensitivity analysis Data were compiled in Excel spreadsheets (Microsoft Corp, Redmond, WA). The risk analysis and simulation software @RISK (Palisade corp., Ithaca, NY, ver. 4.5) for Excel was used to estimate monetary costs attributed to CE infection in humans and livestock. Output variables were defined according to parameters involved in the estimation of direct and indirect costs associated with CE in humans and livestock intermediate hosts (Table 4). Distributions were assigned based on the most likely range for each variable. Median and 2.5 and 97.5 percentiles (95% credible intervals, CIs) were calculated for each output variable. Monte Carlo simulation using a Latin Hypercube approach with 10,000 iterations was performed to model parameter uncertainty. A sensitivity analysis was conducted using stepwise linear regression of the estimated costs against the input parameter values to assess the impact of each input parameter on the overall cost estimate. A separate sensitivity analysis was run excluding losses related to asymptomatic/non-healthcare seeking human CE cases. 10.1371/journal.pntd.0001915.t004 Table 4 Annual direct and indirect costs associated with CE in humans and livestock in Iran. Category Median cost (US $) 95% CI HUMAN Costs of hepatic CE 593,485 410,640–818,157 Costs of pulmonary CE 261,800 189,390–340,775 Costs of CE in liver and lung 75,420 53,198–100,919 Costs of CE in other organs 101,456 70,080–139,730 Direct costs of CE 1,097,950 855,548–1,381,656 Indirect costs of CE§ 372,613 188,873–576,448 Indirect costs of CE¶ 97,527,670 9,712,122–206,574,100 Total costs of human CE§ 1,470,564 1,158,458–1,817,444 Total costs of human CE¶ 98,625,620 10,739,470–207,912,300 * SHEEP Direct costs of CE 12,524,960 4,047,542–22,354,430 Indirect costs of CE 59,036,660 4,047,542–22,354,430 Total costs of sheep CE 71,551,620 16,585,770–152,227,400 * GOAT Direct costs of CE 1,074,601 608,845–1,610,484 Indirect costs of CE 6,031,210 1,271,019–12,306,230 Total costs of goat CE 7,105,811 2,235,714–13,586,770 CATTLE Direct costs of CE 9,992,240 6,412,567–13,777,960 Indirect costs of CE 47,920,830 18,608,570–84,215,220 Total costs of cattle CE 57,913,070 27,012,570–96,117,080 BUFFALO Direct costs of CE 131,108 114,636–148,589 Indirect costs of CE 787,311 314,762–1,273,489 Total costs of buffalo CE 918,418 445,066–1,403,014 CAMEL Direct costs of CE 13,433 6,201–20,886 Indirect costs of CE 586,974 175,347–1,140,535 Total costs of camel CE 600,406 184,034–1,158,064 All animals Direct costs 23,726,340 14,323,200–34,387,130 Indirect costs 114,363,000 51,049,920–196,475,100 Total costs of animal CE 138,089,300 69,524,500–226,669,800 Direct costs of CE in human and animals 24,824,290 15,425,180–35,444,500 Indirect costs of CE in human and animals § 114,735,600 51,377,930–196,922,400 Indirect costs of CE in human and animals ¶ 211,890,700 96,003,140–344,185,200 TOTAL MONETORY COSTS OF CE IN IRAN § 139,559,900 71,095,360–228,152,000 TOTAL MONETORY COSTS OF CE IN IRAN ¶ 236,714,900 117,690,300–373,694,500 * Assuming government-reported slaughter rates for sheep and goats. § Excluding asymptomatic/non-healthcare seeking human population. ¶ Including asymptomatic/non-healthcare seeking human population. Results Human CE costs Table 4 contains estimates of the annual direct and indirect costs associated with CE in humans in Iran. The cost of surgical treatment for a case of hepatic or pulmonary CE in a public hospital was estimated at US$1,027 (95% CI US$676–1,379) and US$851 (95% CI US$528–1,173), respectively. The corresponding values for surgical treatment of CE in a private hospital were estimated at US$1,911 (95% CI US$1,431–2,387) for hepatic and US$2,458 (95% CI US$1,976–2,939) for pulmonary involvement. The overall annual cost of CE in Iran was estimated at US$232.25 million (95% CI US$103.11–397.84 million). The cost associated with human CE was estimated at US$93.39 million (95% CI US$6.11–222.72 million), of which US$1.09 million (95% CI US$820,000–1.44 million) and US$92.34 million (95% CI US$5.01–221.55 million) were attributed to direct and indirect costs, respectively. Human CE contributed to more than 40% of the total annual cost of CE in Iran. This was mainly due to the impact of human productivity losses in the asymptomatic/non-healthcare seeking population. This figure decreased to 1.1% of the total estimated cost when productivity losses in the asymptomatic/non-healthcare seeking population were excluded. Direct costs of human CE were estimated at 1.2% of the total cost of human disease. However, direct costs accounted for three quarters of the economic losses in surgical CE cases. Livestock associated CE costs Assuming government slaughter values, the median annual cost associated with CE in livestock was estimated at US$132.0 million (95% CI US$61.8–246.5 million), of which US$23.5 million (95% CI US$12.7–36.5 million) was direct and US$108.4 million (95% CI US$45.0–216.9 million) was indirect cost. Sheep and cattle CE were responsible for 48% and 42% of the total economic losses due to livestock CE in Iran, respectively. Direct costs associated with CE in livestock accounted for 10.1% of the overall cost of the disease. Indirect costs associated with CE in livestock were primarily due to losses in fecundity and milk reduction. Indirect costs due to CE in livestock intermediate hosts comprised more than 80% of the total livestock-associated costs of CE and approximately 47% of the overall cost of CE in Iran. Costs associated with sheep and goat CE, assuming the practice of home slaughtering, are found in Table 5. 10.1371/journal.pntd.0001915.t005 Table 5 Estimated monetary losses associated with CE in Iran based on two scenarios for home slaughtering. Scenarios Direct costs, US$ (95% CI) Indirect costs, US$ (95% CI) Direct and indirect costs, US$ (95% CI) Government reported values assuming that 12.8% of sheep and 8.5% of goats are slaughtered annually. Sheep 12,524,960 (4,047,542–22,354,430) 59,036,660 (9,746,846–133,468,100) 71,551,620 (16,585,770–152,227,400) Goat 1,074,601 (608,845–1,610,484) 6,031,210 (1,271,019–12,306,230) 7,105,811 (2,235,714–13,586,770) Total 13,589,560 (5,037,907–23,589,440) 65,067,870 (15,316,950–139,935,100) 78,657,420 (22,988,640–159,876,500) Adjusting for home slaughtering assuming that 25% of sheep and 17% of goats are slaughtered annually. Sheep 25,048,910 (8,168,014–44,242,900) 63,456,400 (12,570,030–140,369,500) 88,505,300 (24,126,530–177,011,800) Goat 2,149,359 (1,225,908–3,259,446) 6,400,930 (1,580,594–12,635,600) 8,550,289 (3,359,383–15,273,460) Total 27,198,270 (10,138,330–46,741,520) 69,857,330 (18,569,920–146,739,300) 97,055,590 (32,653,080–186,131,500) Sensitivity analysis The impact of uncertain parameters on the total monetary burden of CE in Iran and the corresponding regression coefficient values are shown in Figure 1. Productivity losses in asymptomatic individuals, CE prevalence in sheep, and fecundity losses in sheep and cattle had the largest impact on overall cost of the disease (Figure 1a). When productivity losses in asymptomatic/non-healthcare seeking individuals were excluded, fecundity losses and CE prevalence in sheep and cattle had the largest overall impact (Figure 1b). 10.1371/journal.pntd.0001915.g001 Figure 1 Regression coefficients of parameters associated with the total cost of CE in Iran. Discussion Estimating the economic impact of a zoonotic disease is a way of quantifying the significance of the disease in both human and livestock populations. In addition, this type of analysis helps decision-makers prioritize resources for disease control and prevention. The aim of the present study was to estimate the economic impacts of CE in Iran. Findings indicated that CE costs Iran more than US$230 million per year. This is a considerable burden as this equates to about 0.03% of the country's Gross Domestic Product (GDP). A value of 0.03% of the country's GDP is in line with the findings of other studies where this value ranged from 0.003% to 0.04% of GDP (Table 6). 10.1371/journal.pntd.0001915.t006 Table 6 Human and livestock population and the proportion of GDP lost due to CE in different countries. Country Human population (million humans) Livestock population (million animals) Total cost of CE (US$ million) % GDP lost Reference Sheep Goat Cattle Iran 74.7 49.9 22.3 7.1 232.3 0.03 Present study Spain 43.0 22.7 2.9 6.5 200 0.01 [19] Turkey 74.7 25.5 6.3 11.0 89¶ 0.01¶ [18] Tunisia 9.6 7.2§ 1.3 0.8 14.7 0.03 [17] Uruguay 3.2 25.0 0.016§ 10.4 9.0 0.04 [14] Peru 26.2 14.2§ 1.9§ 5.5§ 6.3 0.003* [20] Jordan 4.4 1.2 0.5 0.7§ 3.9 0.04 [16] ¶ Cost of animal CE only. § From FAOSTAT, 2010. * Indirect human losses not accounted for. The overall cost of CE in Iran was estimated to be higher than the CE-associated monetary losses for other countries, including Jordan (US$ 3.9 million), Uruguay (US$ 9.0 million), Tunisia (US$ 14.7 million), Turkey (US$ 89 million- livestock losses only), and Spain (US$ 200 million) [14], [15], [16], [18], [19]. This is partly the result of larger human and livestock populations in Iran compared to the other studied countries (Table 6). Iran is the third most populous and second largest country in the Middle East and has the fourth largest sheep population in the world [36]. However, direct comparison of economic losses associated with CE from different countries is difficult since past studies have used a variety of methodologies to arrive at cost estimates. In previous studies on ruminant echinococcosis economic losses due to CE have been estimated using conventional calculation methods. Livestock CE-related losses were estimated at US$459,660 in the city of Ahwaz [25], at US$421,826 in nine districts of North Khorasan province [24] and at US$51,900 in Ardabil province [26]. Based on the results of this study, the monetary burden of CE in Iran is substantial, especially when indirect costs due to productivity losses in the asymptomatic/non-healthcare seeking population were taken into consideration. Productivity losses for asymptomatic/non-healthcare seeking individuals added about US$ 100 million to the overall cost estimate of CE in the country. This estimate was based on the two community-based ultrasound studies that have been carried out in Iran. However, this was not optimal since both of the studies were conducted in rural/nomadic populations. Nevertheless CE cases are increasingly reported from urban regions. The number of CE cases from rural and urban areas was shown not be significantly different in Iran. Several studies have shown that CE is equally prevalent in rural and urban regions, especially due to the increased recreational/camping activities of the urban population and large migrations of people from rural to the urban/peri-urban regions of the country during last three decades [31], [39]. This same phenomenon has been documented in other countries, including Serbia [40], Croatia [41] and Libya [42]. Like other NTDs prevalent in less developed countries, it appears that CE is being urbanized and can no longer be considered solely as a rural disease [43], [44]. The ratio of community ultrasound prevalence to the annual surgical incidence of CE was 669.3, which is higher than the ratio of 45.4 found in Florida, Uruguay [45], the ratio of 22 to 344 for Turkey [46], [47], and the ratio of 241 for Morocco [47]. However, the value is comparable with the ratio of 405 to 1,889 determined for Libya [47], [48]. While this may mean that the number of asymptomatic/non-healthcare seeking individuals in Iran was overestimated, it also could indicate that health-seeking behavior of Iranians is different from that of people in other countries. Compared to Uruguayans, Turks, and Moroccans, Iranians may have either less access to health care or do not seek health care services provided in the country due to different health-seeking behaviors. Differences in the pathogenicity of E. granulosus genotypes/strains may also explain this dissimilarity since it is generally believed that genotypes of E. granulosus can differ in infectivity and/or clinical severity [49]. By applying the ratios for Turkey (334) and Uruguay (45.4) to the incidence rate of surgical cases in Iran, the prevalence of asymptomatic/non-healthcare seeking cases of CE would be 0.23% and 0.06%, respectively compared to the estimated 0.85% used in this study. A limitation of this study was how to assess productivity losses for those individuals who were not formally employed. Based on limited available data, a 30% productivity loss was assumed for women who are not officially employed outside of the home. This value was chosen because a sick homemaker indirectly affects the entire family's productivity and increases living costs of the family. Indirect costs of CE in humans and livestock accounted for more than 80% of overall monetary losses in this study, which is in agreement with the results of other studies in endemic areas [14], [15], [16], [17], [18], [19], [21]. Indirect costs reflect economic effects of the disease that are often not taken into consideration by agriculture and health officials. Indirect costs associated with human CE treatment were probably underestimated in this study. Additional indirect costs may include expenses associated with travel from a rural area to the city, or from one urban area to another urban area to seek appropriate health care, as well as expenses due to an accompanying spouse or other member of the family. Additional studies are needed in order to provide better evidences of the true impact of indirect losses due to CE in both humans and livestock intermediate hosts. Availability of high quality epidemiological and economic data is crucial for improving the accuracy of the estimation. Lack of age-stratified CE prevalence data for livestock was another limitation of the present study. However, abattoir-based CE prevalence data tends to be underestimated due to the fact that, in Iran, animals that are slaughtered in abattoirs tend to be young and, therefore, have a lower chance of being infected compared to older animals. Another important issue is the unexpectedly low proportion of the sheep and goat population reported to be slaughtered each year (12.8% and 8.5%, respectively). These figures reflect animals that are slaughtered in registered abattoirs, which is almost definitely an underestimation. Many people, especially those living in rural/suburban areas, practice home slaughter. In addition, a number of unregulated abattoirs also exist within the country. However, the extent of slaughtering outside official channels is not fully understood and needs to be investigated. To account for the practice of home slaughter, a second scenario was considered assuming that 25% and 17% of sheep and goat populations are slaughtered every year, respectively. As expected, this second scenario resulted in both increased direct and indirect costs for these species (Table 5). However, the overall effect of the second scenario on the total monetary cost of human and animal CE was relatively small (i.e., a 7.7% increase from US$236.7 million to US$254.9 million). Regarding the high proportion of camel population reported to be slaughtered each year (29.7%) that seems very high for such a long-lived animal, we retrieved camel data from official sources (Statistical Center of Iran). Underestimation of the total population of camels is quite probable because of the very traditional nature of camel farming in the country and illegal import of camels across the eastern border. Findings of the present study indicate that CE imposes a substantial economic impact on Iran. Reduction of human and livestock infection through implementation of CE control programs is necessary to reduce the economic burden of CE on the country. Cost-benefit analysis of different control programs is now possible in light of present knowledge on the economic losses associated with CE in Iran. However, because comparing monetary costs in different countries with different socioeconomic statuses is often not optimal, a complementary analysis of the non-monetary burden of CE is recommended to compare CE burden in different geographical regions. In addition, evaluation of the non-monetary burden of the disease and measurement of cost per DALY averted by the control campaigns is recommended. Therefore, a paper evaluating CE-associated DALYs in Iran is currently in preparation. This is the first study to evaluate monetary losses due to human and livestock CE in Iran. However, additional research is needed to improve CE monetary burden estimates and to develop uniform methodologies for assessment [17], [50]. Supporting Information Checklist S1 STROBE checklist. (DOC) Click here for additional data file.
Author and article information
Journal
Journal ID (nlm-ta): Iran J Parasitol
Journal ID (iso-abbrev): Iran J Parasitol
Journal ID (publisher-id): IJPA
Journal ID (pmc): IJPA
Title:
Iranian Journal of Parasitology
Publisher:
Tehran University of Medical Sciences
ISSN
(Print):
1735-7020
ISSN
(Electronic):
2008-238X
Publication date
(Print):
Apr-Jun 2018
Volume: 13
Issue: 2
Pages: 310-316
Affiliations
Author notes
Article
Publisher ID: ijpa-13-310PMC ID: 6068365
PubMed ID: 30069216
SO-VID: ca8d9c70-65d8-4967-9604-1998df0c11ed
Copyright © Copyright© Iranian Society of Parasitology & Tehran University of Medical Sciences
License:
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
History
Date
received
: 25
January
2017
Date
accepted
: 19
August
2017
Categories
Subject:
Short Communication
ScienceOpen disciplines: Parasitology