The endemic diseases combat agents (EDCA) are professionals who work in public health preventing and fighting diseases present in the environment, such as dengue fever, Chagas’ disease, leishmaniasis, and malaria [1]. Their job includes inspecting houses, empty lots, warehouses, and commercial establishments, searching for outbreaks of endemic diseases. They also manipulate and apply larvicides and insecticides to fight vectors and instruct the population regarding the prevention and treatment of infectious diseases [2].

The co-exposure to physical and chemical risks are occupational hazards that must be considered regarding this profession. Authors [3] reported that the EDCA are the health professionals most exposed to pesticides, as they are exposed to it from preparing the solution to applying it. The contamination may be through skin absorption and breathing, especially among the agents that spray the pesticides [4]. However, they are not exposed to pesticides alone, but also to noise from the automatic pump sprayers and heavy ultra-low volume (ULV) sprayers. Although the noise level is reported in a few studies related to pesticide exposure, its assessment is advisable.

Besides the occupational risks related to physical and chemical agents, there are also the ergonomic, social, biological, and accident risks [5] - [12].

Regarding the damages to health, a study pointed out that the main diseases and symptoms reported by the EDCA are the risks of skin cancer, pain from work-related repetitive strain injury and musculoskeletal disorders, as well as the risks of headache and dizziness [13].

Studies have shown damage to the peripheral and central auditory system of populations exposed to pesticides [7] [14] - [25]. However, in most studies, the noise was either not present or its exposure was not considered. In addition, some studies have addressed the effects of pesticides on the vestibular system in humans [15] [26] and in guinea pigs [27] [28].

Hence, this study aimed to evaluate the vestibular functions in endemic diseases combat agents.

Thirty-three (33) EDCA performed the vestibular evaluations; 36.3% of them

Source: Authors [29] [30].

had alterations in the exams, of which 5 (15.2%) presented with right peripheral vestibular deficit dysfunction and 4 (12.1%) with left peripheral vestibular deficit dysfunction. Irritative peripheral vestibular dysfunction was observed in 9% of the cases (Figure 1). Statistical analysis revealed p = 12/33 = 0.364, demonstrating prevalence rate of altered results.

The ages of EDCA were separated into three age groups: up to 50 years old, from 51 to 60 years old, and over 60 years old. The proportion of normal cases is higher (75%), with 25% being the proportion of altered cases (up to 50 years). Among agents aged between 51 and 60 years, the proportion of normal cases dropped to 70% and that of altered cases increased to 30%. Among agents over the age of 60, the proportion of normal cases was very low (20%), while the proportion of altered cases increased to 80%. When correlating the results of vestibular exams with the age of the participants, Fisher’s exact statistical test

showed no relationship, since the p-value = 0.1132.

The results show of the vestibular evaluations took into account the handling time of the pesticide. A higher proportion of normal cases (70%) among participants with shorter exposure time (up to 30 years) was noted, however, when comparing the exposure time to pesticides, up to 30 years and with more than 30 years of exposure, the Fisher’s Exact test showed that the result was not significant at a significance level (p = 0.2825).

The following researchers showed no changes: positional nystagmus, eye movement calibration, spontaneous open-eyed and gaze nystagmus, pendular tracking test, optokinetic and post-rotational nystagmus. Observed changes occurred in the spontaneous closed eyes nystagmus research and in the caloric test. Twelve individuals (36.3%) presented with peripheral vestibular dysfunctions, nine cases with deficitary peripheral vestibular dysfunction (27.3%), and three cases (9%) with irritative peripheral vestibular dysfunction. The vestibular examination was normal in 21 cases (63.7%).

Nystagmus was observed in seven participants in the spontaneous closed eyes nystagmus study. The prevalence rate of spontaneous closed eyes nystagmus was 21.2% and the prevalence ratio was 2.3; hence, the presence of spontaneous closed eyes nystagmus among participants who presented alterations in the vestibular evaluations was twice as high as among participants who presented no alterations. However, through Fisher’s Exact test, there was no statistically significant relationship between the altered tests and the spontaneous closed eyes nystagmus results (p = 0.1970).

Figure 2 shows the auditory and vestibular complaints presented by the study participants. It is noted that 30.3% of participants complained of tinnitus and dizziness, and 33.3% complained of hypoacusis.

Legend: NVE = normal vestibular exam; RPDVD = right peripheral deficit vestibular dysfunction; LPDVD = left peripheral deficit vestibular dysfunction; IPVD = irritative peripheral vestibular dysfunction; RIPVD = right irritative peripheral vestibular dysfunction; LIPVD = left irritative peripheral vestibular dysfunction.

Fisher’s Exact test, at a significance level of 0.05 (5%), revealed no significant relationship between the vestibular examination results and the complaints, when the two were compared (Table 2).

Table 3 shows the results obtained in pure tone audiometry with the results obtained in the vestibular exams. The Mann-Whitney non-parametric test, at a significance level of 5% (0.05), showed a significant difference between the thresholds for the right ear at the frequency of 4000 Hz (p = 0.0494). Therefore, the participants who presented worse hearing thresholds in the right ear at the frequency of 4000 Hz also presented altered results in the vestibular examinations.

The vestibular evaluation findings showed alterations in the exams in 36.3% of the endemic diseases combat agents. Among the participants, 15.2% had exams

Legend: RE = right ear; LE = left ear; NVE = normal vestibular exam; AVE = altered vestibular exam. Non-parametric Test Mann-Whitney (p = value significant*).

suggestive of right deficitary peripheral vestibular dysfunction and 12.1% suggestive of left deficitary peripheral vestibular dysfunction. Irritative peripheral vestibular dysfunction was observed in 9% of the cases. These findings point to the fact that all exam deficits due to vestibular dysfunction were peripheral.

Peripheral vestibular dysfunction is characterized by changes in normal patterns and the absence of signs of dysfunction indicating a central lesion. Deficitary peripheral vestibular dysfunctions are correlated with vestibular alterations where there is a total or partial decrease in vestibular function, and generally have a worse prognosis compared to irritative peripheral vestibular dysfunctions [31].

The results did not show alterations in the positional nystagmus, eye movement calibration, spontaneous and gaze nystagmus, pendular tracking test, optokinetic and rotational nystagmus. However, the alterations were observed in the caloric test and the survey of spontaneous closed eyes nystagmus. Alterations in the caloric test were observed in a study with populations exposed to pesticides, as well as in the research of positional nystagmus and/or vertigo [15]. The result of this last test was not observed in the present study.

Some authors report that the only vestibular test that evaluates each maze is caloric, being a valuable resource for otoneurological diagnosis [32]. It consists of the stimulation of the external ear canal by introducing hot/cold air/water, which heats and cools the lateral semicircular canal wall, generating endolymph convection currents and promoting deviation of the stimulated semicircular canal dome.

All participants presented only with alternations in the spontaneous closed-eye nystagmus, with no alterations in the spontaneous open-eye nystagmus and the gaze nystagmus. This indicated that none presented central alteration. In the spontaneous closed-eye nystagmus survey, 7 participants presented with the same, 3 presented with a normal vestibular exam, and 4 with alteration in vestibular exams. The presence of spontaneous closed-eye nystagmus can be observed in healthy individuals. Spontaneous closed-eye nystagmus in healthy individuals can be considered normal if the result of the slow component angular velocity (SCAV) does not exceed 7˚/s [29] [30]. Only one participant presented SCAV above 7˚/s, whose right horizontal spontaneous closed-eye nystagmus result associated with the caloric test result (right labyrinthine predominance 9%) showed irritative peripheral vestibular dysfunction.

In a study, irritative peripheral vestibular dysfunction was observed in 88.8% of 18 rural workers exposed to organophosphate insecticide-type pesticides [15]. A study showed the population exposed to various types of pesticides with varying degrees of toxicity, such as Manzate (54.2%), which has toxicology grade III, Folidol (33.3%), Tamaron (27.1%), and Gramaxone (25%), that has a type I toxicology degree and considered highly toxic. Most of the studied population was female (72.2%) and with a mean age of 36.6 years (range 16 to 59 years old). In addition, it was not mentioned in the study whether this population had combined exposure to noise [15]. This did not corroborate the findings of the present study, considering that among participants who presented vestibular dysfunction, the deficitary type was more evident (27.4%).

The present study showed no significant relationship between exposure to pesticides and noise and the occurrence of altered vestibular examinations.

Regarding auditory and vestibular complaints, 30.3% of the participants in the present study presented tinnitus and dizziness and 33.3% complained of hypoacusis. Tinnitus complaint was observed in other studies with populations exposed to pesticides and noise [17] [19] [23] [33].

A study revealed 57% of participants to have tinnitus [33]. One study showed a similar occurrence of tinnitus (52.08%) [17]. Another study found that 28.05% of workers simultaneously exposed to pesticides and noise complained of tinnitus, increasing this incidence among workers who presented alterations in the audiometry (60.87%) [19]. The occurrence of tinnitus in another study reported an incidence of 46% among agricultural workers [23].

Studies have shown that dizziness complaint is a recurrent clinical symptom in populations exposed to pesticides [15] [34].

Dizziness is characterized by a sensation of alteration in body balance, either rotatory (vertigo) or non-rotatory (body instability), and it appears when there is interference in the normal functioning of the body balance system, which may be of peripheral or central origin [35].

Authors have reported that long-term exposure to pesticides may affect the central processing of sensory information for body balance as well as the sensory and somatosensory/vestibular systems [34].

In the present study, no statistically significant relationship was observed between the dizziness complaint and the vestibular exams (p = 0.5366). The dizziness complaint presented by the study participants could not be attributed to the altered vestibular exams. However, it is undisputed that exposure to chemical agents may affect the postural balance of exposed populations [34] [36], and that the age factor may contribute to the increase in dizziness [37] [38].

A statistically significant difference was noted between the auditory pure tone thresholds of the right ear obtained at 4000 Hz and the results of the altered vestibular exams. This finding may be justified by the anterior and posterior labyrinth intertwined from an anatomo-physiological stand-point, consistent with Cochlear-Vestibular Syndrome. This known fact in the literature justifies the importance of researching the integrity of the auditory system through the auditory exams along with the vestibular exams [39].

In a study, hearing normality was verified by conventional audiological evaluation, among 61.14% of 18 rural workers exposed to organophosphate insecticides. While 38.8% presented hearing alterations, 22.22% of the workers presented hearing loss at the frequencies of 6000 and 8000 Hz, and 16.67% presented sensorineural hearing loss [15].

The occurrence of vestibular dysfunction was observed in more than 1/3 of the studied population and related to anterior and posterior labyrinth alteration (Cochlear-Vestibular Syndrome). There was no sign of central vestibular alteration in any of the participants. The most common peripheral alteration was of the deficit type, revealing the chronicity of the condition.

The authors declare no conflicts of interest regarding the publication of this paper.

de Souza Alcarás, P.A., Zeigelboim, B.S., Corazza, M.C.A., Lüders, D., Marques, J.M. and de Lacerda, A.B.M. (2021) Vestibular Function Evaluation in Endemic Diseases Combat Agents. Health, 13, 144-156. https://doi.org/10.4236/health.2021.132013