**1. Introduction**

Mosquitoes have a higher impact than any other bug because of the diseases they spread. Mosquito-borne infections are a substantial hazard to human health and are one of the leading causes of morbidity and mortality worldwide [1–5]. The mosquito vector, the human host, and the environment are all involved in the development of these diseases [6].

Over one billion people are affected and over one million people die each year because of vector-borne diseases, the majority of which are caused by mosquitos [5]. Zika virus, Malaria, Dengue Fever, Japanese Encephalitis, Yellow Fever, West Nile Virus, Filariasis, and Rift Valley Fever are the communal mosquito-borne diseases MBDs [5, 7–9]. In Saudi Arabia, dengue fever, malaria, and rift valley fever are among the MBDs reported by many researchers in many parts of the kingdom [10–20].

Complex factors influence mosquito dispersal and abundance, including MBDs [21, 22]. Climate parameters such as temperature, relative humidity, and rainfall, on the other hand, are critical determinants of mosquito vector survival, production, growth, abundance, and dispersal [23–26]. The temperature has been proven to have an impact on mosquito abundance, activity, and presence in both temporary and permanent habitats. It has an impact on the parasite's development and the time it takes from egg to adult mosquito [27–31]. Rainfall has a similar effect on mosquito dispersion by giving or sustaining more breeding grounds. On the other hand, clearing out small breeding sites and lowering the temperature, has a detrimental impact [6, 31]. The number of females laying eggs, the number of eggs laid, the frequency of feeding, and the metabolic rate of adult mosquitos are all affected by changes in relative humidity. Aside from climatic considerations, mosquito distribution and abundance were substantially impacted by the spatial distribution of breeding regions, habitat, land use patterns, preferred hosts, and flight distance [32, 33]. The association between climatic parameters such as temperature, relative humidity, and rainfall has been studied in several research [34–37]. However, no research has been done on the impact of climatic parameters (temperature, relative humidity, and rainfall) on mosquito abundance in Saudi Arabia's Eastern Province.

The objective of this research is to determine how seasonal abundance and distribution of individual mosquito vectors (Culex, Anopheles, and Aedes) alter in connection to climatic parameters such as temperature, relative humidity, and rainfall in Saudi Arabia's Eastern Province.

#### **2. Material and methods**

#### **2.1 Study area**

The Eastern Province of Saudi Arabia is bordered to the north by the Northern Province, Kuwait to the northeast, and the Sultanate of Oman to the south by the Arabian Gulf. It has a variety of geographical characteristics, including sandy soil, coastal lowlands, industrialized areas, and agricultural areas. It is characterized by an arid climate with a temperature rising from 15°C in January to a maximum of about 42°C in the August-September period. The average annual rainfall ranges from around 100 mm in the north and northeast during winter to less than 10 mm in Rub al-Khali [38].

Several environmental factors influence the abundance and distribution of mosquitoes in the area. These factors include temperature, relative humidity, and precipitation, the presence of palm gardens/vegetables that hold a large volume of rainwater, widespread salt marshes, and irrigation ditches. Poor sanitary sewerage system in the areas also causes the accumulation of large volume of sewage water which serves as good breeding habitat for mosquitoes in the study area [18]. 322 larvae breeding sites were assessed for the presence of mosquito larvae in eight locations. However, only 206 sites (64.0%) found positive with mosquito larvae. Those locations include;

*Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*

Abu Main (5 sites), Umm As Sahik (19 sites), Safwa (10 sites), Al-Awjam (22 sites), Dammam (12 sites), Al-Qatif and its surrounding area (81 sites), Buqayq (32 sites) and Al-Sarar (25 sites). Those sites showed their diverse ecological characteristic and abundance of mosquito species **Figure 1**.

#### **2.2 Data collection**

The larval and adult mosquito data was collected in collaboration with the Ministry of Health branch in Dammam. Data collection was carried out from January to December 2014. The monthly data collected were compiled for each study site for 2014. A sampling of mosquito larvae was carried out in various

**Figure 1.** *Map showing study sites in Eastern Province, Saudi Arabia [39].*

breeding habitats (ditches, sewages, stagnant and surface waters) by taking 3-5 scoops of water for each sampling location to check for the presence of larvae [18]. Mosquito larvae were identified using a dissecting microscope. Electric flycatchers and cow sheets with spray are applied to catch adult mosquitoes mainly from cattle barns.

The meteorological data of temperature, relative humidity, and precipitation were obtained from the Presidency of Meteorology and Environment (PME) Dammam for the period noted above. Temperature is defined as a mean average of minimum and maximum temperature, measured in degree Celsius (°C). Relative humidity (RH), expressed in percentage (%), is the average monthly humidity based on the daily records. Precipitation/rainfall is the amount of rainfall in the month, measured in millimeters.

**Figure 2.** *Diagram showing steps processes of the study.*

*Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*

#### **2.3 Data analysis**

Data was analyzed to determine the relationship between mosquito abundance and climatic factors. Bivariate analysis was carried out to determine the relationship between mosquito abundance and each climatic factor (temperature, relative humidity, and rainfall). Multivariate regression analysis was performed to identify the overall effect of temperature, relative humidity, and rainfall in mosquito abundance. A descriptive analysis was carried out to determine the trends of mosquito abundance and climatic factors. The results of the bivariate analysis are expressed in Pearson correlation coefficient using sigma plot software (Systat Software Inc).

A systematic procedure was carried out to study mosquito distribution and abundance in Eastern Province, Saudi Arabia **Figure 2**.

### **3. Results**

**Table 1** shows the number of mosquito larvae and adult mosquitos collected in the Eastern Province of Saudi Arabia during the study year (2014). From January to December 2014, 31041 mosquito larvae and 2036 adult mosquitos were collected across all sites. Qatif and the surrounding area had the most adults and larvae, followed by Awjam and Umm As Sahik.

Culex mosquito larvae accounted for 20345 (65.54%) of the total 31041 mosquito larvae collected, whereas Aedes and Anopheles mosquito larvae accounted for 5641 (18.17%) and 5055 (16.28%) respectively. In contrast, 1528 (75.05%) of the 2036 adult mosquitos collected were Culex, while 508 (24.95%) were Anopheles. Throughout the year, however, no adult Aedes mosquitos were collected at any of the sites. In each study site, **Table 2** showed the relative distribution and number of larval and adult mosquitos. The larval and adult Culex were found in many habitats throughout the research area, according to the findings.

Some mosquito species were captured as larvae but not as adults in this investigation. In the study region, Aedes mosquitos were gathered as larvae but not as adults throughout the year. Adult Culex and Anopheles were also not collected throughout the year in Buqayq and Al-Sarar. During the study period, neither larval nor adult Anopheles were obtained from the Dammam area **Table 2**. The relationship between mosquito larvae (Culex, Anopheles and Aedes) abundance and climatic factors of temperature, relative humidity, and rainfall demonstrated in **Figure 3**. A high number of Culex larvae were observed throughout December, February, March, and April, whereas many Anopheles larvae were gathered during November, December, March, April, and June. The high number of Aedes larvae were observed during November, December, and February, as shown. **Figure 3** also revealed that a significant number of total mosquito larvae were collected in the months of November, December, February, March, and April.

**Figure 4** depicts the link between adult mosquito abundance (Culex and Anopheles) and climatic parameters (temperature, relative humidity, and rainfall). Specifically, throughout the months of December, February, and March, many adult Culex and Anopheles were gathered. This figure also shows that in November, December, January, February, March, and April, 2014 a large number of total adult mosquitos were seen. The statistical analyses performed between larval and adult mosquito abundance and climatic factors are given in **Table 3**. These statistical analyses were executed for Abu Main, Umm As-Sahik, Safwa, Al-Awjam, Dammam,


 *Time-based dispersal and abundance of larvae and adult type in Eastern Province, Saudi Arabia 2014.*


*Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*

#### **Table 2.**

*Spatial distribution and abundance of larvae and adult by mosquito type.*

and Al-Qatif, including Buqayq and Al Sarar for larvae, with the exception of Buqayq and Al Sarar for the adult since no adult mosquitoes were collected from these sites during field visits. **Table 3** illustrated the negative correlation between temperature and Culex (except in Umm-As Sahik), Anopheles, and Aedes larvae. However, positive relationship between relative humidity and rainfall except in some sites. The multivariate regression analysis, on the other hand, explained that the three climatic factors together were responsible for 33.1% (R2 = 0.331), 54.6% (R2 = 0.546), and 86.6% (R2 = 0.866) of the variance on Culex, Anopheles and Aedes larvae, respectively, in Eastern Province of Saudi Arabia.

**Table 3** also clearly shows that adult Culex mosquito abundance had a negative correlation with temperature except in Safwa. Specifically, in Umm As Sahik, Awjam, and Qatif and the surrounding area, a strong negative correlation between adult Culex and the temperature was observed with correlation values of −0.726, −0.717, and −0.850, respectively. However, positive correlation with relative humidity, with highest correlation values of 0.716, 0.773, and 0.592 in Umm As Sahik, Awjam, and Qatif and surrounding area, respectively, but a negative correlation with relative humidity in Safwa site. It is also evident from **Table 3** that adult Culex mosquito abundance had a moderate to low positive correlation with rainfall except (negative) in Safwa and Dammam.

Similarly, **Table 3** clearly shows that adult Anopheles mosquito abundance had a strong negative correlation with temperature. The table also demonstrated a negative correlation between Adult Anopheles abundance and rainfall (except

**Figure 3.** *The temporal relationship between climatic factors and mosquito larvae.*

#### **Figure 4.**

*The temporal relationship between climatic factors and adult mosquitoes.*

in Umm-As Sahik and Al-Awjam) while a strong positive correlation with relative humidity in all sites.

The current study also demonstrated the combined effect of the three climatic factors on the abundance of adult Culex and Anopheles mosquitoes. The multivariate regression model for three climatic factors (temperature, RH, and rainfall) explained 86% (R2 = 0.860) and 73.9% (R2 = 0.739) of the variance in adult Culex and Anopheles mosquito abundance, respectively. It showed also that the three climatic factors together were responsible for 33.1% (R2 = 0.331), 54.6% (R2 = 0.546) and 86.6% (R2 = 0.866) of the variance on Culex, Anopheles and Aedes larvae, respectively. This means that 86% and 73.9% of the variance are accounted for the three parameters and the remaining 14% and 26.1% are attributed to other factors such as the presence of the vegetation, waste materials, water reservoirs, ditches, and others. Comparing the two adults, the adult Anopheles mosquito was more influenced


**Table 3.**

*The correlation coefficient between climatic factors, and abundance of adult and larval.*

*Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*

by other environmental factors than by climatic factors compared to the adult Culex mosquito which is more influenced by climatic factors than by other environmental factors in the Eastern Province, Saudi Arabia.

Overall, both Culex and Anopheles larvae had a moderate negative association with temperature in Saudi Arabia's Eastern Province, but Aedes larvae had a substantial negative correlation with temperature. On the other hand, low, moderate, and a strong positive correlation were observed between Anopheles, Culex, and Aedes larvae, and relative humidity, respectively. Rainfall and the three mosquito larvae types in the study area had a low positive link, according to the current study. Adult Culex and Anopheles both displayed a strong negative connection with temperature, with the highest values of −0.876 and −0.802, respectively, and a substantial positive correlation with relative humidity, with correlation values of 0.650 and 0.627, respectively. In Eastern Province, Saudi Arabia, both adult mosquitoes had a favorable link with rainfall in general.

#### **4. Discussion**

Understanding the impact of climatic conditions on mosquito distribution and abundance is critical for mosquito control efforts. The range and abundance of individual mosquito types are influenced by climatic conditions such as temperature, relative humidity, and rainfall [32, 34].

In the Eastern Province of Saudi Arabia, this study gave a clear explanation of the relationship between mosquito abundance and meteorological conditions. The response of larvae and adult mosquitoes to each climatic factors varied depending on season and site as shown in graphical **Figures 3** and **4**, and statistical analyses in **Table 3**. Other environmental factors, such as the presence of vegetation, irrigation activities, and poor environmental sanitation, were also shown to have an impact on the distribution and abundance of individual mosquito vectors in the study. In several ecosystems in the research region, the Culex mosquito was found to be the most abundant and widely spread. The reasons for the larval and adult Culex's widespread range and abundance in Saudi Arabia's Eastern Province are similar to prior investigations [10–20]. Agricultural expansion, the presence of irrigation ditches/canals, ponds, and extensive farming, according to Alahmed [18], contribute to the wide dispersion and incidence of mosquitos in Saudi Arabia's Eastern Province. Muturi et al. [40] observed that the presence of floating vegetation in the aquatic habitat, turbid/polluted water, and the presence of water reservoirs such as irrigation canals/dits in the area all influence the distribution of Culex larvae and have been linked to the presence of Culex larvae.

Calhoun et al. [41] reported a higher number of Culex larvae in oily/rusty water when compared to clean water. Similarly, Ohta and Kaga [42] found that substantial irrigation activities enhance mosquito growth, lengthen mosquito annual growing periods, and raise mosquito maximum generation numbers by altering natural water in their environment. It was also shown that irrigation systems not only aid mosquito growth during dry seasons but also help to stabilize growth during rainy seasons. Temperatures ranging from 16.4 to 27.7°C are ideal for Culex larvae's growth and survival, while temperatures ranging from 17.5 to 35°C and 16.4 to 22.3°C are ideal for Anopheles and Aedes larvae development and survival, respectively. Temperatures of 16.4 to 22.4°C, on the other hand, support substantial growth and survival of adult Culex and Anopheles. On the other hand, the overall data of larvae/adult clearly

#### *Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*

indicate that temperatures ranging from 16.4 to 27.7°C are ideal for larvae development and survival, whereas temperatures ranging from 15 to 27.7°C promote a high abundance and spread of adult mosquito in Eastern province.

High environmental temperatures greater than 30°C decreases the survival of the Culex mosquito [43]. However, Hopp and Foley [44] and Tun *et al.* [27] reported that high temperatures speed up the growth and survival of larval and adult stages of the Culex mosquito. Similarly, the increase in environmental temperatures decreases the survival and development of larval and adult stages of Anopheles mosquito [45]. Bayoh and Lindsay [29] also found a decrease in Anopheles larvae survival as environmental temperature increases. However, Minakawa *et al.* [34] reported that the influence of temperature on Anopheles mosquito was significant. The influence of temperature on mosquito development, survival, and productivity is difficult to predict at a precise range, as evidenced by these and other studies [23]. During the summer, the average temperature in the research region exceeded 35o C, which is unfavorable for mosquito larval and adult growth. In July, when the temperature was 36.9°C, just a few larval and adult mosquitos were found, as shown in **Figures 3** and **4**. Overall, high larval and adult mosquitos were collected at temperatures ranging from 16.4 to 27.7°C and 15 to 27.7°C, respectively. Temperatures between 20 and 29°C have been found to be advantageous for mosquito growth in several studies [23, 36–37, 46]. The study also demonstrated that moderate relative humidity influences the increase of the larval and adult stages of the mosquito. Abundant Culex and Anopheles larvae were observed at average relative humidity that ranges from 34 to 58%. Unlike to this, a high number of Aedes larvae was collected at mean relative humidity that ranges from 43 to 58%. On the other hand, a high number of both adult Culex and Anopheles mosquitoes were observed at a relative humidity that ranges between 44 and 58% (**Figures 3** and **4**).

The survival and developmental phases of mosquitoes are influenced by relative humidity, according to various research. The lifespan of mosquitos is shown to increase as humidity rises, while high humidity increases mosquito density and abundance [18, 23, 25, 35–37]. Costa *et al.* [30] observed that when the temperature and relative humidity are both lower, the number of female Aedes mosquitos depositing eggs and their egg production (oviposition) increases. In contrast, Hopp and Foley [44] reported that as temperature and humidity rise, the Aedes mosquito produces more eggs and larvae counts. Low humidity, on the other hand, was associated with a lower number of Culex, Anopheles, and Aedes larvae, as well as a lower abundance of adult Culex and Anopheles mosquitos, according to this study. As the relative humidity drops throughout the summer, only a small number of larval and adult mosquitos are gathered. In all study sites, the number of larval and adult mosquitos increased throughout the months of October, November, December, January, February, and March, 2014 when relative humidity was high (**Figures 3** and **4**).

The effect of rainfall on mosquito larvae was not seen in the current investigation **Figure 3**. Even though the fact that the average annual rainfall in Eastern Province is 5 mm, the influence of rainfall on adult mosquitos was visible in the number of adult mosquitos during the wet months. In comparison to the dry seasons, higher adult mosquito activity was recorded during the rainy months of January, February, March, and April **Figure 4**. Rainfall has a beneficial or negative impact on mosquito numbers, either by supplying more/maintaining breeding places or by flushing mosquito larvae from small breeding sites [25, 31, 35–37, 47, 48].

The bivariate analysis indicated that the response of the larval and adult mosquito vectors of Culex and Anopheles as well as Aedes larvae to each climatic factors such as temperature, relative humidity, and rainfall varied by site. As shown in **Table 3**, both stages of the larval and adult forms of an individual mosquito of Culex and Anopheles including Aedes larvae were found negatively correlated with temperature while positively correlated to relative humidity and rainfall.

Similarly, from the multivariate regression analysis, the response of the individual mosquito vectors of both stages that are the larval and adult Culex and Anopheles as well as Aedes larvae, to the combined effect of the three climatic factors varied, depending on the site. From the regression model, it is understood that Aedes larvae were more influenced by climatic factors than Culex and Anopheles larvae, which were more affected by other environmental factors. It seems that Culex and Anopheles larvae are more influenced by the presence of vegetation, waste material, water reservoirs, and ditches. The presence of floating and terrestrial vegetation, poor environmental sanitation, and extensive irrigation activities that create water reservoirs such as ditches are among the major environmental factors for mosquito abundance and their wide distribution in many habitats [39, 41, 42, 49].

The vast spread of Culex larvae could be attributable to favorable climatic conditions in the research area, as well as their capacity to develop and survive in a variety of aquatic breeding sites. They can also thrive in polluted and saline aquatic habitats. Aside from water quality, the presence of floating vegetation and waste materials (such as plastics, papers, old tires, and rags) in the aquatic habitat also contributed to the wide distribution and abundance of Culex larvae, as these environmental factors provide appropriate access for adult Culex mosquitos to lay their eggs and for their larvae to develop and survive. Irrigation activities in the study area also contribute to the larvae's distribution and abundance by creating water reservoirs such as ditches where mosquito larvae can breed.

The presence of some mosquito types as larvae but not as an adult in some sites may be due to the differences in adult behavior such as feeding and resting behavior (as some mosquito species are indoor feeders and indoor resting while others are outdoor feeders and indoor resting) attributed to unavailability of adult mosquitoes and they did not come close to the trapping or sampling location placed outside houses during the data collection period [18]. The other reason for the unavailability of adult mosquitoes was limited access to the human residence since adult mosquitoes were collected from rooms of cattle during the morning time (day).

## **5. Conclusion**

Mosquito control programs benefit greatly from an awareness of the effects of climatic conditions on mosquito vectors. Mosquito abundance can be predicted by anticipating temperature, relative humidity, and rainfall, and then present and future mosquito control measures can be planned and implemented. As a result, this research provides comprehensive information on the impact of climatic conditions on the abundance of specific mosquito vectors in Saudi Arabia's Eastern Province. However, further research is needed to determine the impact of global warming, irrigation activities, land use, and the biological characteristics of mosquito breeding sites on mosquito distribution and abundance before large-scale control methods can be implemented.

*Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern… DOI: http://dx.doi.org/10.5772/intechopen.104615*
