Abstract
Background
This research was conducted to assess the arthropod-related mortality in Iran for the period 2016–2023.
Methods
The information on arthropod-related mortality was collected from the Iranian Ministry of Health and Medical Education. The descriptive analyses and charts were created using R version 3.4. ArcMap GIS 10.8.1 software was utilized to design and produce the study map. Temporal trends were examined using the Mann–Kendall test and Theil–Sen slope estimator, while seasonal patterns were assessed via the Hirsch–Slack modified test, Poisson regression with Fourier terms (to estimate annual percent change), chi-square goodness-of-fit, Kruskal–Wallis, Rayleigh’s test, and STL decomposition. A p-value < 0.05 was considered statistically significant.
Results
The highest arthropod-related mortality rates were observed in the southern and southeastern provinces, particularly Sistan and Baluchestan and Hormozgan, likely due to favorable ecological conditions supporting high densities of medically important arthropods. Among all recorded cases, the most frequent cause of death was ICD-10 code X22 (contact with venomous arthropods), accounting for 219 fatalities. A pronounced seasonal pattern was evident, with mortality peaking significantly during the warmer months of the year.
Conclusions
Effective reduction of arthropod-related mortality requires timely, location-specific public health strategies, particularly in summer and in southern and southeastern Iran.
Keywords: Arthropod vectors, Vector-borne diseases, Insect bites and stings, Mortality
Background
Iran's diverse ecosystems and rich arthropod fauna make the country particularly susceptible to health problems from venomous bites, stings, and other arthropod-related injuries [1, 2]. Arthropod bites and stings pose a significant public health challenge worldwide due to their capacity to induce immediate toxic effects and facilitate the transmission of infectious diseases [3]. Arthropods, especially mosquitoes, rank among the most lethal organisms affecting human health, mainly because of the diseases they transmit. Each year, diseases transmitted by mosquitoes lead to more than one million fatalities, with malaria responsible for approximately 597,000–608,000 deaths, predominantly in children under the age of five, and over 263 million cases documented in 2023 [4]. Each year, around 50,000 cases of scorpion stings are reported in Iran. Some epidemiological studies have shown that scorpion stings are the leading cause of envenomation in Iran, particularly in the southwestern regions [5, 6]. Spider bites are uncommon; however, they can sometimes result in severe systemic effects, including pulmonary edema, cardiac irregularities, coagulopathies, and death. Bites from various other arthropods, such as centipedes and millipedes, happen infrequently and are seldom lethal, generally leading to localized pain and inflammation [7]. Thus, the investigation of arthropods and the assessment of health risks arising from human interaction with them should be regarded as a fundamental priority, since these organisms are key contributors to the transmission of vector-borne pathogens, the induction of allergic and toxic responses, and the broader challenges faced by public health systems. This study aimed to investigate the documented arthropod-related mortality in Iran during 2016 to 2023, utilizing national mortality data categorized under the International Statistical Classification of Diseases and Related Health Problems (ICD-10) [8]. This study provides a comprehensive overview of the epidemiological patterns, temporal distribution, and potential public health implications of arthropod-related mortality, thereby contributing to a deeper understanding of their burden and informing future strategies for prevention and control.
Methods
Study area
Iran is located in southwestern Asia and covers a wide range of geographical and climatic conditions. The country encompasses diverse ecosystems, including humid and temperate regions along the northern Caspian Sea coast, arid and semi-arid areas in the central plateau and eastern regions, mountainous areas in the west and northwest, and warm coastal environments in the south and southeast. The northern regions are characterized by a humid subtropical climate, whereas central and eastern Iran are predominantly dry and desert-like. The western and northwestern parts of the country are largely mountainous, with colder climates and higher precipitation, while southern and southeastern regions experience hot climates influenced by the Persian Gulf, Gulf of Oman, and desert environments. These geographical and climatic variations contribute to differences in arthropod diversity, distribution, and potential exposure risks across the country [9].
Data collection
The data on arthropod-related mortality in Iran from 2016 to 2023 were obtained through official correspondence with the National Mortality Registration Portal of the Ministry of Health and Medical Education of Iran, classified according to ICD-10 codes [8].
Data analyses
To account for differences in provincial population size, crude mortality rates were calculated and expressed as deaths per 100,000 population for 2016–2023. Crude mortality rates were calculated for the entire study period (2016–2023) by dividing the total number of recorded deaths in each province during the study period by the corresponding provincial population and multiplying by 100,000. Provincial population estimates from the 2016 National Population and Housing Census were used as the population denominator because this was the most recent officially available provincial population dataset. Thus, the reported crude mortality rates represent cumulative mortality rates for the 2016–2023 study period rather than annual mortality rates.
Temporal trends were assessed with the non-parametric Mann–Kendall test applied to the annual death counts, both for the series as a whole and separately for each disease group, with the magnitude of change quantified by the Theil-Sen slope estimator and its distribution-free 95% confidence interval. Because the monthly series is strongly seasonal, the seasonal (Hirsch-Slack) modification of the Mann–Kendall test was additionally applied to the 96 monthly observations, treating the twelve Iranian (Jalali) months as blocks. Monthly death counts were then modelled with a Poisson time-series regression containing a linear term for calendar time and two pairs of Fourier (harmonic) terms representing annual and semi-annual periodicity; the annual percent change (APC) was derived from the time coefficient as (exp(12*beta)−1) × 100. Overdispersion was assessed by the ratio of the Pearson chi-square statistic to its residual degrees of freedom (1.17), and residual serial correlation by the Ljung-Box test at lag 12. Seasonality was evaluated with a chi-square goodness-of-fit test against a month-length-weighted uniform distribution, the Kruskal–Wallis test across the four seasons, the Rayleigh test of circular uniformity applied to individual dates of death, and STL (seasonal-trend decomposition by loess) of the monthly series. All analyses were performed in R version 4.3.3; two-sided p-values below 0.05 were considered statistically significant.
Result
Arthropod-borne viral fevers
Unspecified arthropod-borne viral fever (ICD-10: A94)
The ICD-10 code A94 is identified as "Unspecified arthropod-borne viral fever." This covers: Fever due to an unspecified arbovirus and infection resulting from an unspecified arbovirus. It is often termed "Arboviral fever NOS" or "Arbovirus infection NOS." According to recorded statistics, 11 deaths in Iran have been attributed to an unknown arbovirus infection transmitted through arthropod bites. Of these cases, 27% were men and 73% were women, with an average age of 46.9 years. The fatalities were reported in Sistan and Baluchestan (n=5; 0.180 deaths per 100,000 population), Semnan (n=1; 0.142), Isfahan (n=1; 0.020), Kohgiluyeh and Boyer-Ahmad (n=1; 0.140), Tehran (n=1; 0.008), Chaharmahal and Bakhtiari (n=1; 0.106), and Mazandaran (n=1; 0.030) provinces. Nearly half of the cases (45%) occurred in Sistan and Baluchestan Province. The temporal distribution of recorded deaths during 2016–2023 showed considerable variation, with the highest mortality observed in 2022 (n=3), followed by 2023, 2021, and 2017 (n=2 each), while 2018 and 2016 each recorded one death.
Crimean-Congo hemorrhagic fever (ICD-10: A98.0)
Crimean-Congo Hemorrhagic Fever (CCHF) is a severe viral hemorrhagic fever. It is primarily transmitted through tick bites or contact with infected animal or human body fluids. Between 2016 and 2023, 63 deaths attributable to CCHF were recorded in Iran. Of these cases, 76.2% (n=48) were male, and 23.8% (n=15) were female, with a mean age of 17.5 years. Mortality was reported across various Provinces, with the highest numbers recorded in Kermanshah (n=6; 0.307 deaths per 100,000 population), Sistan and Baluchestan (n=6; 0.216), Chaharmahal and Bakhtiari (n=2; 0.211), Fars (n=9; 0.186), Yazd (n=2; 0.176), and Khorasan Razavi (n=10; 0.155). Additional fatalities occurred in South Khorasan (n=1; 0.130), Kerman (n=4; 0.126), Gilan (n=3; 0.119), Hormozgan (n=2; 0.113), Golestan (n=2; 0.107), Ardabil (n=1; 0.079), Alborz (n=2; 0.074), Isfahan (n=3; 0.059), Hamadan (n=1; 0.058), Lorestan (n=1; 0.057), Tehran (n=5; 0.038), West Azerbaijan (n=1; 0.031), East Azerbaijan (n=1; 0.026), and Khuzestan (n=1; 0.021).
The temporal distribution of recorded deaths showed variation over the study period, with the highest mortality observed in 2017 (n=12), followed by 2018 (n=11), 2023 (n=9), 2022 and 2019 (n=7 each), 2020 and 2016 (n=6 each), and 2021 (n=5).
Protozoal disease
Malaria caused by Plasmodium falciparum, including mixed infection caused by P. falciparum with other Plasmodium species (ICD-10: B50)
Two deaths attributed to the disease were documented in Iran, both occurring in males from Sarbaz and Iranshahr Counties in Sistan and Baluchestan Province. Based on the provincial population, the crude mortality rate in Sistan and Baluchestan was 0.072 deaths per 100,000 population during 2016–2023. One case was in a neonate and the other in a 72-year-old individual.
Malaria caused by P. falciparum with cerebral complications (ICD-10: B50.0)
Plasmodium falciparum, presenting with cerebral complications, led to the death of a 53-year-old man in 1400, with the province of occurrence not specified.
P. falciparum with unspecified complications (ICD-10: B50.9)
In Iran, three deaths—two males and one female—were attributed to P. Falciparum with unspecified complications. The mean age of the deceased was 46 years. One fatality each was recorded in Fars and Tehran provinces, corresponding to crude mortality rates of 0.021 and 0.008 deaths per 100,000 population, respectively. The province of occurrence for the remaining case was not reported.
Plasmodium vivax, including mixed infections with other Plasmodium Species (excluding P. falciparum) (ICD-10: B51)
A fatal case of malaria caused by P. vivax, including mixed infection with other Plasmodium species, was reported in a 55-year-old man from Sistan and Baluchestan province. The corresponding crude mortality rate was 0.036 deaths per 100,000 population during 2016–2023.
Malaria caused by P. vivax with rupture of spleen (ICD-10: B51.0)
A case of this disease was reported in 2017 in a 44-year-old woman from Sistan and Baluchestan province. The corresponding crude mortality rate was 0.036 deaths per 100,000 population during 2016–2023.
P. vivax malaria with other complications (ICD-10: B51.8)
Two male fatalities due to P. vivax malaria with additional complications were documented in Sistan and Baluchestan Province. The mean age of the deceased was 27.5 years, corresponding to a crude mortality rate of 0.072 deaths per 100,000 population during 2016–2023.
Other parasitologically confirmed malaria (ICD-10: B53)
A death due to other parasitologically confirmed malaria was documented in Sistan and Baluchestan Province. The case involved a 37-year-old man from Iranshahr County who died in 2023. Based on one recorded fatality during 2016–2023, the corresponding crude mortality rate was 0.036 deaths per 100,000 population.
Unspecified malaria (clinically diagnosed without parasitological confirmation) (ICD-10: B54)
A total of six deaths from unspecified malaria (ICD-10: B54) were reported in Iran. The deceased included four males and two females, with a mean age of 55.1 years. Four fatalities were recorded in Sistan and Baluchestan Province (0.144 deaths per 100,000 population), while one fatality occurred in Khorasan Razavi Province (0.016 deaths per 100,000 population). The province of occurrence for the remaining case was not reported. These fatalities occurred in 2017 (n=1), 2021 (n=2), 2022 (n=1), and 2023 (n=2).
Visceral leishmaniasis (Kala-Azar) and post-Kala-Azar dermal leishmaniasis (ICD-10: B55.0)
Visceral leishmaniasis (VL; Kala-Azar) is endemic in Iran, particularly in the northwestern regions, whereas post-Kala-Azar dermal leishmaniasis (PKDL) is considered rare, with only a few sporadic cases reported in Iran. Three fatalities were reported, including two in Fars Province (0.041 deaths per 100,000 population) and one in Ilam Province (0.172 deaths per 100,000 population). The deceased comprised a 72-year-old man and two children aged 11 months and 11 years, with all fatalities occurring in 2019.
Cutaneous leishmaniasis (ICD-10: B55.1)
Although deaths from cutaneous leishmaniasis are extremely rare worldwide, a single fatality was reported in Tehran Province in 2019, involving a 72-year-old man. The corresponding crude mortality rate was 0.008 deaths per 100,000 population.
Bitten or stung by non-venomous arthropod (ICD-10: W57)
Arthropods in Iran remain an important public health concern. Between 2016 and 2023, a total of 41 fatalities were documented, including 63.4% males and 36.6% females, with a mean age of 35.31 years. Deaths were reported from 20 provinces, with the highest numbers recorded in Sistan and Baluchestan (n=7; 0.252 deaths per 100,000 population), North Khorasan (n=2; 0.232), Hamadan (n=4; 0.230), Kerman (n=7; 0.221), and Chaharmahal and Bakhtiari (n=2; 0.211). Other affected provinces included Hormozgan (n=3; 0.169), East Azerbaijan (n=5; 0.128), Kermanshah (n=2; 0.102), Bushehr (n=1; 0.086), Khuzestan (n=4; 0.085), Gilan (n=2; 0.079), Qazvin (n=1; 0.079), Kurdistan (n=1; 0.062), Lorestan (n=1; 0.057), Golestan (n=1; 0.053), Khorasan Razavi (n=3; 0.047), Fars (n=2; 0.041), Alborz (n=1; 0.037), Isfahan (n=1; 0.020), and Tehran (n=1; 0.008) Provinces. Temporally, mortality varied over the study period, with the highest number of deaths occurring in 2017, 2018, 2019, 2020, 2023 (n=6 each), followed by 2016 (n=5), and the lowest in 2021 and 2022 (n=3 each).
Injury, poisoning and certain other consequences of external causes
Contact with venomous spiders (black widow spiders and tarantulas) (ICD-10: X21)
One fatality resulting from contact with venomous spiders was reported in 2017 and 2019 in Golestan Province, involving a 58-year-old man. The corresponding crude mortality rates were 0.05 deaths per 100,000 population in Golestan Province.
Contact with scorpions (ICD-10: X22)
Scorpion stings represent a significant public health concern in Iran. Between 2016 and 2023, a total of 219 deaths due to scorpion envenomation were recorded, including 113 males (51.6%) and 106 females (48.4%). The distribution of fatalities and corresponding crude mortality rates across provinces was as follows: Sistan and Baluchestan (n=49; 1.77 deaths per 100,000 population), Hormozgan (n=16; 0.90), Kohgiluyeh and Boyer-Ahmad (n=6; 0.84), Kerman (n=16; 0.51), Ilam (n=2; 0.34), Khuzestan (n=12; 0.25), Lorestan (n=2; 0.11), Chaharmahal and Bakhtiari (n=1; 0.11), Kermanshah (n=2; 0.10), East Azerbaijan (n=1; 0.03), Fars (n=1; 0.02), Isfahan (n=1; 0.02). These findings indicate a clear geographic pattern, with the highest mortality burden concentrated in southern and southeastern provinces, particularly Sistan and Baluchestan and Hormozgan. The highest number of fatalities was recorded in 2022 (n = 42), followed by 2019 (n = 33), 2020 (n = 31), 2016 (n = 26), 2018 (n = 23), 2017 (n = 21), and the lowest figures were observed in 2021 and 2023 (n = 19 each).
Contact with wasps (including yellow-jacket wasps), hornets, and honeybees (ICD-10: X23)
During the study period (2016–2023), a total of 55 fatalities were reported due to stings from honeybees, hornets, and wasps (including yellow jackets). Of these, 74.5% were males (n=41) and 25.5% were females (n=14), with a mean age of 39 years. The distribution of fatalities and corresponding crude mortality rates varied considerably across provinces. The highest mortality rates were observed in Ardabil (n=3; 0.236 per 100,000 population), followed by Sistan and Baluchestan (n=6; 0.216), Chaharmahal and Bakhtiari (n=1; 0.211), Kerman (n=3; 0.190), Hamadan (n=2; 0.173), Bushehr (n=2; 0.172), Hormozgan (n=2; 0.169), West Azerbaijan (n=5; 0.153), East Azerbaijan (n=4; 0.128), Kurdistan (n=2; 0.125), and Fars (n=6; 0.124). Additional cases were documented in Isfahan (n=5; 0.117), Alborz (n=1; 0.111), Golestan (n=1; 0.107), Kermanshah (n=2; 0.102), Zanjan (n=1; 0.095), Yazd (n=1; 0.088), Markazi (n=1; 0.070), Khuzestan (n=2; 0.064), Khorasan Razavi (n=1; 0.062), and Tehran (n=4; 0.038). Annual mortality fluctuated throughout the study period, with the highest number of deaths recorded in 2019 (n = 9), followed by 2016 and 2020, each with 8 deaths.
Contact with venomous centipedes and millipedes (tropical) (ICD-10: X24)
A fatal case resulting from contact with venomous centipedes and millipedes was reported in East Azerbaijan Province in 2019, with a corresponding crude mortality rate of 0.026 deaths per 100,000 population.
Contact with other known venomous arthropods, including ants and caterpillars (ICD-10: X25)
A total of seven fatalities were documented as a result of contact with other known venomous arthropods, including ants and caterpillars. Of these fatalities, 57.14% were males and 42.86% were females. Three deaths were reported in Sistan and Baluchestan Province (0.108 deaths per 100,000 population), while single fatalities were recorded in Kermanshah (0.051), Fars (0.021), Kerman (0.032), and Qazvin (0.079) provinces. Temporally, two deaths occurred in 2017, one death was recorded in each of the years 2018–2020, and two deaths occurred in 2023.
Temporal trends and seasonality
As shown in Table 1, the Mann–Kendall test detected no statistically significant monotonic trend in arthropod-related mortality. The overall annual series was flat (Kendall’s τ = 0.25, p = 0.454), and the same conclusion held for the monthly series (p = 0.949), for the seasonal (Hirsch–Slack) Mann–Kendall test (Z = 1.20, p = 0.231), and for each of the four disease groups. The formal seasonality tests are collected in Table 2. Every test rejected a uniform distribution of deaths—the twelve-month chi-square (χ2 = 155.4), the four-season chi-square (χ2 = 117.2), the Kruskal–Wallis test (χ2 = 22.6), the Rayleigh test, and the likelihood-ratio test for the harmonic terms (χ2 = 177.5) were all significant at p < 0.001. Deaths peaked in Tir (June–July, n = 71) and fell to a minimum in Dey (December–January, n = 7), a peak-to-trough ratio of 10.1; summer accounted for 43.2% of deaths and winter for 5.5%. Table 3 reports the Poisson time-series regression, in which monthly counts were modelled with a linear time term (t) and two Fourier harmonic pairs (s1, c1, s2, c2). Consistent with Table 1, the time term was not significant (IRR = 1.001, p = 0.558), confirming a stable long-term level, whereas the harmonic terms captured the strong seasonal signal quantified in Table 2 (annual percent change +1.3%, 95% CI −2.9% to +5.6%).
Table 1.
Mann–Kendall trend analysis of arthropod-related mortality in Iran (2016–2023), overall, by disease group, and for the monthly series
| Series | Kendall's τ | Z | p | Theil–Sen slope (95% CI) |
|---|---|---|---|---|
| All arthropod-related deaths (annual) | 0.25 | 0.75 | 0.454 | 0.69 (−3.00 to 5.50) |
| Arthropod-borne viral fevers | −0.04 | 0.00 | 1.000 | 0.00 (−1.75 to 1.67) |
| Protozoal disease | 0.29 | 0.88 | 0.379 | 0.50 (−1.00 to 2.00) |
| Bites and stings by non-venomous arthropods | −0.11 | −0.29 | 0.772 | 0.00 (−0.75 to 0.14) |
| Injury, poisoning and certain other consequences of external causes | 0.00 | 0.00 | 1.000 | −0.04 (−5.50 to 4.50) |
| All deaths (monthly, n = 96) | −0.00 | −0.06 | 0.949 | 0.00 (−0.02 to 0.02) |
| All deaths (monthly, seasonal Mann–Kendall) | – | 1.20 | 0.231 | – |
Table 2.
Tests of seasonality in arthropod-related mortality in Iran (2016–2023)
| Test | Statistic | df | p |
|---|---|---|---|
| Chi-square goodness-of-fit (12 Jalali months) | 155.36 | 11 | <0.001 |
| Chi-square goodness-of-fit (4 seasons) | 117.23 | 3 | <0.001 |
| Kruskal–Wallis (annual counts by season) | 22.56 | 3 | <0.001 |
| Rayleigh test of circular uniformity | 77.89 | – | <0.001 |
| Likelihood-ratio test for harmonic terms | 177.47 | 4 | <0.001 |
Table 3.
Count time-series regression of monthly arthropod-related mortality in Iran (2016–2023)
| Term | Estimate | SE | IRR | IRR (lower 95% CI) | IRR (upper 95% CI) | p |
|---|---|---|---|---|---|---|
| (Intercept) | 1.1545 | 0.1091 | 3.1723 | 2.5618 | 3.9283 | <0.001 |
| t | 0.0010 | 0.0018 | 1.0010 | 0.9976 | 1.0045 | 0.558 |
| s1 | 0.6794 | 0.0844 | 1.9727 | 1.6718 | 2.3278 | <0.001 |
| c1 | -0.8596 | 0.0954 | 0.4233 | 0.3511 | 0.5104 | <0.001 |
| s2 | 0.2097 | 0.0796 | 1.2334 | 1.0552 | 1.4416 | 0.008 |
| c2 | -0.2002 | 0.0785 | 0.8186 | 0.7019 | 0.9546 | 0.011 |
T linear time term, s1/c1 and s2/c2 annual and semi-annual Fourier terms, IRR incidence rate ratio
Discussion
The provincial distribution of mortality in Iran, as shown in Fig. 1, reveals significant regional differences in the number of deaths across ICD-10 categories. According to the data, Sistan and Baluchestan Province (n=134; 4.83 deaths per 100,000 population) had the highest mortality rate associated with arthropod contact. This was followed by Hormozgan (n=56; 3.15), Kohgiluyeh and Boyer-Ahmad (n=8; 1.122), Kerman (n=32; 1.01), and Chaharmahal and Bakhtiari (n=8; 0.84) Provinces, which ranked second to fifth, respectively. In contrast, significantly lower rates are observed in the northern and central regions of the country, including Mazandaran (n=1; 0.03 deaths per 100,000 population, Markazi (n=1; 0.07), Zanjan (n=1; 0.09), Tehran (n=13; 0.10), and Qazvin (n=2; 0.157). This geographic gradient may reflect differences in ecological and climatic conditions across provinces. As shown in Fig. 2, cumulative arthropod-related mortality rates were generally higher in southern and southeastern provinces and lower in northern and central regions of Iran.
Fig. 1.
Distribution of arthropod-related mortality in Iran by province of residence (rows, ordered by total deaths) and exact ICD-10 code (columns), 2016–2023. Cell colour and label indicate the number of deaths. X22: Contact with scorpions; A98.0: Crimean-Congo haemorrhagic fever (CCHF); X23: Contact with wasps (including yellow-jacket wasps), hornets, and honeybees; W57: Bitten or stung by non-venomous arthropods; A94: Unspecified Arthropod-Borne Viral Fever, X25: Contact with other known venomous arthropods, including ants and caterpillars; B54: Unspecified Malaria (Clinically Diagnosed without Parasitological Confirmation); B55.0: Visceral Leishmaniasis (Kala-Azar) and Post-Kala-Azar Dermal Leishmaniasis; B50.9: P. falciparum with Unspecified Complications; B51.8: P. vivax malaria with other complications; B50: Malaria caused by Plasmodium falciparum, including mixed infection caused by P. falciparum with other Plasmodium species; B50.0: Malaria Caused by P. falciparum with Cerebral Complications; X24: Contact with venomous centipedes and millipedes (tropical); X21: Contact with venomous spiders (black widow spiders and tarantulas); B55.1: Cutaneous leishmaniasis; B53: Other Parasitologically Confirmed Malaria; B51.0: Malaria caused by P. vivax with Rupture of Spleen; B51: Plasmodium vivax, Including Mixed Infections with Other Plasmodium Species (Excluding P. falciparum)
Fig. 2.
Cumulative arthropod-related mortality in Iran per 100,000 population from 2016 to 2023. Darker colors indicate higher mortality rates
The highest recorded mortality from contact with arthropods is associated with X22 (n=219), A98.0 (n=63), X23 (n=55), and W57 (n=41) according to ICD-10 codes (Fig. 3). A stable long-term trend in arthropod-related mortality was corroborated by the Mann–Kendall test over the study period. Although Fig. 4 shows some inter-group variability over time, these fluctuations were not statistically significant.
Fig. 3.
Total arthropod-related mortality in Iran by exact ICD-10 code, 2016–2023. X22: Contact with scorpions; A98.0: Crimean-Congo haemorrhagic fever (CCHF); X23: Contact with wasps (including yellow-jacket wasps), hornets, and honeybees; W57: Bitten or stung by non-venomous arthropods; A94: Unspecified Arthropod-Borne Viral Fever, X25: Contact with other known venomous arthropods, including ants and caterpillars; B54: Unspecified Malaria (Clinically Diagnosed without Parasitological Confirmation); B55.0: Visceral Leishmaniasis (Kala-Azar) and Post-Kala-Azar Dermal Leishmaniasis; B50.9: P. falciparum with Unspecified Complications; B51.8: P. vivax malaria with other complications; B50: Malaria caused by Plasmodium falciparum, including mixed infection caused by P. falciparum with other Plasmodium species; B50.0: Malaria Caused by P. falciparum with Cerebral Complications; X24: Contact with venomous centipedes and millipedes (tropical); X21: Contact with venomous spiders (black widow spiders and tarantulas); B55.1: Cutaneous leishmaniasis; B53: Other Parasitologically Confirmed Malaria; B51.0: Malaria caused by P. vivax with Rupture of Spleen; B51: Plasmodium vivax, Including Mixed Infections with Other Plasmodium Species (Excluding P. falciparum)
Fig. 4.
Annual arthropod-related mortality in Iran by disease group, 2016–2023
A strong seasonal pattern was observed in arthropod-related mortality, with a marked peak during the warmer months. Nevertheless, despite this pronounced summer predominance, a notable increase in mortality during the autumn and winter months has been observed from 2018 to 2023 (Fig. 5). Milder and shorter winters can prolong the activity season of disease vectors and venomous arthropods, potentially extending the transmission window for arboviral diseases into the cooler months. The observed trend may be consistent with the influence of climate variability; however, no causal relationship can be inferred from the present descriptive study, and further ecological and climatological investigations are needed to examine this hypothesis.
Fig. 5.
Temporal trends in arthropod-related mortality in Iran (2016–2023). Numerals denote the Iranian (Jalali) month; the black line is a loess smoother
Arthropod-borne viral fevers
The high crude mortality rate of CCHF in provinces including Kermanshah, Sistan and Baluchestan, Chaharmahal and Bakhtiari, Fars, Yazd, and Khorasan Razavi may be associated with a combination of factors such as high-risk occupational exposure (involving livestock and slaughtering) [10], the existence of tick vectors including Hyalomma sp. (i.e., Hyalomma marginatum, H. dromedarii, H. anatolicum, H. lusitanicum, H. asiaticum) and Rhipicephalus sanguineus, Haemaphysalis concinna, and infected livestock [11–16], favorable ecological conditions for vector activity [17], and, in some cases, endemic border-trade dynamics such as Pakistan and Afghanistan [17, 18]. Therefore, it is essential to implement strengthened surveillance, control of livestock movement, tick management, and targeted educational initiatives for high-risk occupations in these provinces.
Parasitic protozoan diseases
Sistan and Baluchestan Province has the highest malaria burden in Iran, particularly due to P. vivax and, to a lesser extent, P. falciparum [19]. Several factors, including cross‑border transmission, high vector activity, and rural occupational exposure, may contribute to this burden [20, 21]. Although malaria-related mortality and severe complications such as splenic rupture are relatively uncommon, the continued transmission of malaria in Sistan and Baluchestan underscores the need to strengthen vector control, enhance surveillance, and ensure early diagnosis and prompt treatment.
Leishmaniasis remains an important vector-borne disease in Iran, with cutaneous leishmaniasis (CL), including both anthroponotic (ACL) and zoonotic (ZCL) forms, accounting for the vast majority of reported cases. Between 1983 and 2012, an average of 18,884 CL cases were reported annually, corresponding to an incidence of approximately 32 cases per 100,000 population, although the true burden is likely underestimated because of underreporting. In contrast, visceral leishmaniasis (VL) occurs less frequently but is associated with substantially greater morbidity and mortality. About PKDL, during 2001–2002, two confirmed cases of PKDL caused by Leishmania infantum were identified in the northwestern part of Iran [22].
The persistence of endemic foci is influenced by a combination of ecological conditions, reservoir hosts, vector distribution, human activities, and environmental changes [23]. Three cases of mortality attributed to ICD-10 code B55.0 were documented in the present study, involving patients aged 11 months, 11 years, and 72 years. Although the number of fatalities was small, these findings suggest that severe outcomes may occur in both pediatric and older populations. This observation is consistent with previous studies showing that young children and older adults are at increased risk of severe visceral leishmaniasis because of age-related differences in immune competence [24–27]. The only fatal case of cutaneous leishmaniasis was also observed in an older adult (72 years), further suggesting that advanced age may contribute to unfavorable outcomes in the rare instances of fatal CL.
Bites and stings by non-venomous arthropods
Although non-venomous arthropod bites and stings accounted for a smaller proportion of arthropod-related mortality compared with venomous exposures, they still represent a relevant public health concern in Iran. The occurrence of fatalities across 20 provinces indicates a widespread geographic distribution. This broad distribution suggests that fatal outcomes are influenced not only by arthropod presence but also by regional differences in exposure patterns [5, 28, 29]. However, these factors were beyond the scope of the present study, and further ecological, epidemiological, and socio-demographic research is required to clarify their potential roles in shaping these mortality patterns.
Injury, poisoning, and other consequences of external causes
Overall, the findings demonstrate a substantial geographic heterogeneity in mortality associated with arthropod-related injuries and envenomation in Iran. Scorpion stings represented the largest mortality burden among venomous arthropod-related causes, with the highest crude mortality rates observed in southern and southeastern provinces, particularly Sistan and Baluchestan and Hormozgan, highlighting these regions as priority areas for targeted prevention and control strategies. Fatalities from wasp, hornet, and honeybee stings, although accounting for a smaller number of deaths, appeared to exhibit distinct spatial patterns, with higher rates observed in Ardabil. This might suggest the influence of local ecological conditions, occupational exposures such as beekeeping, and outdoor activities that could increase human contact with these insects [29]. Deaths from spider bites in Iran have only been reported in Golestan province, likely due to greater human exposure in these areas, resulting from a wider distribution of spiders in the northern regions [30]. Although fatalities from centipede, millipede, ant, and caterpillar exposures were rare compared with scorpion stings, their occurrence across several provinces indicates that these lesser-known arthropods still contribute to the overall mortality burden highlight the need for increased awareness among healthcare providers and the public regarding the potential severity of these envenomations.
Conclusion
This study provides a national overview of arthropod-related mortality in Iran during 2016–2023, demonstrating substantial geographic and temporal variation. The reported Arthropod-Related Mortality, in descending order of frequency, was injury, poisoning, and certain other consequences of external causes (n=283); CCHF (n=63); bites or stings by non-venomous arthropods (n=41); malaria (n=17); unspecified arthropod-borne viral fever (n=11); and leishmaniasis (n=4). Scorpion-related mortality accounted for the largest burden among arthropod-related mortality, with higher mortality rates mainly observed in southern and southeastern provinces. These findings provide a clearer picture of the national burden and geographic distribution of arthropod-related mortality in Iran and may serve as a basis for future epidemiological and ecological investigations.
Acknowledgements
The authors would like to thank the Ministry of Health and Medical Education of Iran for providing access to the National Mortality Registration Portal and supporting this research.
Author contributions
P.S-A and A.A: Conceptualization, supervision, methodology, and manuscript drafting. R. E: methodology, statistical analysis, and critical revision of the manuscript. E. M-A and E.K: Study design, Data collection, Conceptualization, supervision, methodology, and manuscript drafting. All authors approved the final version of the manuscript.
Funding
This study received funding from Ardabil University of Medical Sciences, Ardabil, Iran, through Grant No. 404000302.
Data availability
No datasets were generated or analysed during the current study.
Declarations
Ethics approval and consent to participate
This study was approved by the Iranian National Committee for Ethics in Biomedical Research (Approval ID: IR.ARUMS.REC.1404.268).
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
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Data Availability Statement
No datasets were generated or analysed during the current study.