VL is a pathology considered endemic in America continent. 97% of cases reported in 2020 happened in Brazil, other cases were reported in Argentina, Bolivia, Colombia, Paraguay, Venezuela and Uruguay [9]. In Brazil, the region with the highest VL incidence is the Northeast, about 61% (1767) of incidence as compared with another region in Brazil as shown in the figure1.
In 2016 VL incidence in Northeast was 53% (1490) and 49% (1824) in 2017. In the follow years, 2018 and 2019 incidence increased to 57% (1735;1241 respectively), also in 2020 the incidence has risen to 59% (959). The highest incidence per 100.000/inhab was reported in 2017. Northeast reported 3.2/100.000 cases, North there were 4.3/100.000, Midwest region 1.1/100.000, Southeast 1/100.000 and South region with 0.1 /100.000 inhabitants.
There was a decrease in reported cases in 2020. Cases per 100.000 inhabitants in Northeast were 1.7, North 1.6, Midwest 0.5 and Southeast 0.3. The region south no cases were reported in 2020 [2]. The Northern and Northeastern region presented the highest rates of the disease, because the regions have an upward uncontrolled urban development accompanied by precarious housing and sanity conditions. These parts of the country, suffer from the lack of effective preventive measures. In addition, climate and regional vegetation favor the population grown of Lutzomyia, as well as more mosquitoes in these regions than in others, so the most intense infection occurs there.
The Figure 1 shows case evolution of the VL notification according to macro-region of Brazil. Brazilian Northeast is leader in notification, second is Southeast followed by North and Midwest. South region has the lowest incidence. In 2017 and 2018 the Northeast shows that there was a high notification and it has a drop in cases in 2020, which may be related to underreporting due to the overload in heath sectors caused by the Covid-19 pandemic. Lack of priority is common in neglected diseases and can led to the reduction of epidemiological control measures and notifications, which represents a risk to public health, as the disease is spreading without the necessary care to control it [2].
Figure 2 presents incidence coefficient of VL per 100.000 inhabitants in the state of Pernambuco, from 2015 to 2020. The VL incidence in Pernambuco in 2015 was 1.3, higher than 2016 which was 0.8. In the year of 2017 the incidence increased to 1.0 also, in 2018 incidence elevated to 1.2. Sequentially, in 2019 there was a decline to 1.1 and to 0.7 in 2020. [4].
Pernambuco has a notification index of 175, 118, 185, 200, 181 and 113 respectively for each year. In 2016 there was a reduction of 32% in cases in relation to 2015. In three subsequent years case index increased, in 2017 this rise was equitant to 56.8% compared to 2016, in 2018 there was a growth of 8,1% in relation to the previous year. However, in 2019 number of cases reduced 9,5% compared to 2018, additionally to 2020 presenting the smallest number of cases, a decreasing of 37.6%. [2].
The Figure 3 represents data on notifications of VL between 2015 until 2020 divided by macro regions of the state. It was observed that River São Francisco Valley and Araripe macro-region in 2015 had the highest rate compared to other regions. A same profile of VL case incidence in this region was observed in 2016 and 2017. River São Francisco Valley and Araripe macro-region is a region with outstanding agriculture and livestock, where is located the city of Petrolina, the largest fruit production center of the state. Thus, the environment propitiates a favorable ambient for the mosquito reproduction and propagation, increasing rate of infected dogs, humans, and other wild animals that may be a reason the disease spreads quickly [2].
The metropolitan region of Pernambuco presented an increase of case notification in 2018 as showed in Figure 3, evidencing an advance of VL for urban area. In 2019 occurred an outbreak of the disease, which was reduced in 2020. One of the reasons which this region has elevated values, is because high population density, sanitation problem, and history of regular floods [2].
Agreste macro region presented the lowest rate of the VL infected people between 2015 to 2016, showing an increase in the following two years 2017 and 2028 respectively. However, there was a reduction of cases in 2019 and 2020, as can see in the figure 3. The Sertão macro region presented similar profile of VL confirmed cases as compared with Agreste macro-Region.
Sertão macro region demonstrated a relatively controlled oscillation in VL cases, may because this region is marked by drought, sparse vegetation, an area where livestock predominates. So, this region does not present a favorable environment for mosquito to infect a greater number of host as other regions of the state because of the dry weather, high thermal amplitude and little vegetation which reduces the moist places propitious to mosquitos breeding [2].
The mortality average of VL in the state of Pernambuco between 2015 and 2020 was 8.1%. The co-infection of the VL with HIV revealed an increasing during the years (Figure 4). Epidemiological data presented the highest percentage of co-infection incidence in 2020, about 11.5 % patients infected with Leishmaniasis and HIV at the same time [2]. As evidenced in the Figure 4, the mortality of co-infected patients has been rising since 2017, a worrying fact that demands more intense control measures to avoid co-infected patients and consequently reduce mortality [3].
In order to demonstrate VL epidemiological profile, The table 1 summarize the distribution of the variables investigated according to the case notification per year. In relation to sex, it was observed higher prevalence of men infected an average of 67.2% from 2015 to 2020.
As can shows in Table 1, according to age, it was observed a high VL case incidence in children under 10 years old and adults with age between 20 and 59. In relation to VL method of diagnose, laboratorial method is the first choice to confirm the infection. The clinical analysis is especially important in endemic region once the correct diagnostic provides more chance of cure if they follow the suitable treatment. The index of patients that abandoned the treatments is extremely low, there were two patients in 2016 and one in 2020. The percentage of patients that dies due VL is about 12,5% in average between the years 2015 to 2020.
The Figure 5 shows schooling profile of infected patients’ residents in the state of Pernambuco during the study period. According to information from DATASUS, omission about schooling represented 40.3% of the total reported cases. In all years, it was observed an increase in a number of the case of patients with child education, followed by elementary school, high school, illiterate and bachelors. According to the study by Junior and Bezerra may be important to evaluate the fact VL mainly affects people with low education, they related that an illiterate is eight times more likely to be infected by VL. It is worth to mention that there is a high incidence in children under 5 years old who are not yet literate. Due to the elevate omission of schooling information the present study is not conclusive to evaluate the real profile of patient’s education [14]
Currently, in Brazil is adopted the strategy of the National Visceral Leishmaniasis Surveillance and Control Program (PNVCLV) that citing euthanasia as a measure to control the infection in canine reservoirs, as the main measure to prevent transmission of the disease to human. Despite being used, this procedure must follow the current law and it presents many challenges such as lack of resources and infrastructure in small cities around the state, moreover, ethical and emotional issues, which raises the question of how effective this practice really is.
Alternative methods are sought to avoid canine infection such as, vaccination and the use of collars with deltamethrin. These measures should be studies and implemented as prophylactic measures, mainly in regions with high incidence in order to prevent the spread of the disease and consequently, control it [7]. JÚNIOR and BEZERRA explain the spread of the disease is caused by the changes in agrarian structure of Brazil, mosquito adaptation, malnutrition and lack of basic sanitation considering these as main factors that favor urbanization and geographic expansion of VL. In Pernambuco, this factor is quite remarkable due to the socioeconomic situation of the state [14].
The COVID-19 pandemic affected surveillance and control actions across the Brazil, moreover, actions such as field searches to identify mosquitos’ outbreaks and early diagnosis in dogs and humans, detailed analysis of endemic cities also were affected. Until 2019 the disease was endemic with a higher incidence even if there is a strategy to control neglected diseases, the state did not have a significant reduction in cases, which proves that it must increase the vector control measures, identification and treatment of patients. After the COVID-19 pandemic all the rates decreased, what can be related to the underreport. Therefore, plans must be made to contain the disease, especially in endemic regions, with treatment for human, use of collars in dogs and vaccines as a preventive method [3].