Mosquitoes in Cuajiniquil ! Arana 1 ! Mosquito (Diptera: Culicidae) Distribution in Cuajiniquil, Guanacaste, Costa Rica Ah'Shirae Arana University of California, Riverside EAP Tropical Biology and Conservation Program, Spring 2018 8 June 2018 ABSTRACT Understanding mosquito distribution can lower the risk of people affected by mosquito borne illnesses. This two part study aims to present the distribution of potential disease carrying mosquitoes located in Cuajiniquil, Guanacaste, Costa Rica. In the firs t part of the study, I analyzed mosquito oviposition preference by placing receptacles filled with river water in homes and mangroves for nine days. I found no larvae in these experimentally placed containers. In the second part of my study, 137 mosquitoes were captured and identified to species from four different locations of the area. Four genera were identified with Aedes as the most abundant genus . At least eight species were identified including Anopheles punctipennis , a species capable of transmittin g malaria. Keywords: distribution, mosquitoes, Cuajiniquil, Costa Rica, water receptacles La distribuciÂ—n de zancudos (Diptera: Culicidae) en Cuajiniiquil, Guanacaste, Costa Rica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osquitoes are important vectors that transmit deadly diseases. Some of these diseases include dengue fever, malaria and Zika virus. To lay eggs, a female mosquito must acquire special proteins and iron found in the blood of a host (Nayar and Sauerman Jr. 1975). Humans, monkeys, and even pigs serve as potential blood host for the mosquito (Horne 1994). To carry a disease, the mos quito must first bite a host who has already been infected with the virus. When the mosquito receives the harmful pathogen, it can be transmitted to future hosts. In most cases, animals are the primary host of these viruses, but it is humans most affected with the disease (Kilpatrick, A. Marm, et al 2006). There are various host seeking strategies that mosquitoes use in disease transmission. For example, Aedes aegypti who is the host vector of dengue fever, has evolved to use humans as its main source of b lood by sharing human habitats, primarily indoors (Day 2005).
Mosquitoes in Cuajiniquil ! Arana 2 ! Understanding mosquito distribution and abundance is important to be able to take precautionary actions against disease outbreak. Although not all mosquitoes can transmit a virus, knowing the e xact species in an area along with their location abundance is valuable. This information can lead to public health initiatives of mosquito population control in hopes of lowering the number of people at risk of mosquito borne viruses. Although fumigation efforts already take place with chemical insecticide use, it is believed that mosquitoes are starting to develop a resistance to the pesticides used against them (Bisset, et al. 2013). This suggests that the implementation of new control efforts needs to o ccur to lower the risk of future outbreaks from these vectors. There have been various research projects to document the distributions of mosquitoes in Costa Rica. For example, in 2013, eighteen species of mosquitoes were identified from resting sites at Palo Verde Biological Station in Guanacaste, Costa Rica (Burkett Cadena, et. al 2013), with Culex being the primary genus found. In 2018, ovitraps were used to capture and analyze mosquito larvae at the La Selva Biological Station located in the province o f Heredia (Burkett Cadena, et. al 2013). However, there has been scarce research on mosquito distribution for the small fishing town of Cuajiniquil. In this study, I documented the distribution of female mosquito species found in Cuajiiquil to address the following questions: What is the distribution of mosquitoes in Cuajiniquil, Guanacaste, Costa Rica? Will mosquitoes lay eggs in river water receptacles? Where are disease transmitting mosquitoes found? To evaluate these questions, I (1) placed water recept acles filled with river water in homes and mangroves to analyze ovipositon preference (2) sampled and identified adult mosquitoes located in homes, the forest edge, in mangroves, and near Rio Cuajiniquil (3) compared the number of mosquitoes or larvae foun d in these areas to assess where the greatest distribution of species occurs. MATERIALS AND METHODS Study Site: This study took place in Cuajiniquil, a small fishing town of two thousand people located in Guanacaste, Costa Rica. It consisted of two parts in which the first part was conducted for nine days from 10 May 2018 until 19 May 2018 and the second part was conducted for five days from 13 May 2018 until 18 May 2018. Mosquito Larvae Distribution On 10 May 2018, I set out 30 receptacles ( see A ppendix B ) containing river water. The receptacles were small plastic cups of the same size. 15 were placed in mangr oves, located west of the soccer field in Ca ngrejal and 15 were placed around five different homes with permission of the homeowners. I did not place receptacles in areas where they could be washed away by daily high tides. After the receptacles were placed in each location, I checked the river water content to determine wh ether mosquito larvae were present . The receptacles were checked every three days to allow the eggs to hatch into larvae. If the river water was not present in the receptacles during inspection, I refilled the container. I was also mindful to look for any open water receptacle near homes or in the mangroves that contained mos quito larvae to collect and compare the genus of larvae found in other freshwater receptacles versus river water receptacles.
Mosquitoes in Cuajiniquil ! Arana 3 ! Adult Mosquito Distribution in Cuajiniquil For thirty minutes daily, varying between the times of 6:00PM 7:00PM, a randomized number of one, two, or five persons were assigned to one of four locations: inside and outsi de a home, at the soccer f ield (considered to be the forest edge), in the mangroves or near Rio Cuajiniquil to collect adult mosquitoes. Each person received a glas s jar that had been treated with alcohol inside for at least a minute. Each glass jar served as the instrument used to capture as many mosquitoes as possible in a thirty minute increment. Persons were permitted to allow mosquitoes to land on their body if needed to capture them. Volunteers were also allowed to wear DEET or any other form of body protection if desired. All newly found mosquitoes were then placed in individual plastic vials after each capturing session. I carefully placed the mosquitoes in a petri dish one by one to identify to species using a dissecting microscope and a dichotomous key, Mosquitoes: Pictorial Key to United States Genera of Adults (Female) by Harry D. Pratt and Chester J. Stojanovich (See Appendix A). After identifications were completed, the mosquitoes were stored in plastic vials containing alcohol and organized in ziplock bags by assigned number. R ESULTS To understand the first part of this study, Figure 1 demonstrates the distribution of where the 15 river water receptacles were placed in the five homes of Cuajiniquil. The homes were close to each other and located on the east side of the soccer field. After 3 days of observations, results showed that ther e was no difference in larvae formation between the river water receptacles placed in homes and river water receptacles placed in mangroves. In all thir ty river water receptacles, no larvae were found. In one home, I found a total of 20 larvae in two diff erent receptacles I did not experimentally place. Ten occurred in a decorative fish bowl located on the family dining room table and ten came from a bucket filled with water in the patio area. To understand adult mosquito distribution, a total of 137 mosqu itoes were captured over a span of five days in Cuajiniquil, Guanacaste, Costa Rica. 101 mosquitoes were identified belonging to at least 8 different species (Table 1). 4 genera were identified: Aedes, Anopholes, Deinocerites, and Wyeomyia. 36 mosquitoes were not identified due to damage of the specimen. In both homes and the forest edge, Aedes spp (could not further identify) was the most common species identified. In mangroves, the most abundant species was Aedes trieseriatus , and near river Cuajiniquil , Aedes taeniorhynchus and Anopheles punctipennis were two species with the same occurrence. Most mosquitoes were captured in the mangroves. The second location with most mosquitoes captured was the forest edge, however this location also contained 32 of t he 36 specimens that could not be identified. In contrast, the fewest number of captured mosquitoes was near Rio Cuajiniqu il.
Mosquitoes in Cuajiniquil ! Arana 4 ! Figure 1: A map of Cuajiniquil, Guanacaste, Costa Rica showing the locations of river water receptacles placed in five different homes. Table 1: A distribution of the adult mosquito species found in four different areas of Cuajiniquil, Guanacaste, Costa Rica . DISCUSSION In this study, I sought to determine the distribution of mosquitoes in Cuajiniquil, Guanac aste, Costa Rica. Understanding egg laying preferences of mosquitoes and where they are
Mosquitoes in Cuajiniquil ! Arana 5 ! heavily populated can be an essential resource for public health initiatives especially if the species of a disease transmitting mosquito is known. My results demonstra te an important step forward in understanding the mosquito distribution of Cuajiniquil, a small town known to have cases of the mosquito borne illness, dengue fever. To address mosquito larvae distribution, it is important to note the time of year the stud y took place. It was conducted in the middle of May which is the transition of dry season to wet season. This could be a plausible explanation as to why zero larvae were found in any of the river water filled receptacles, as mosquitoes such as the Anopheles genus are known to prefer rainy and moist conditions to oviposit (Minakawa 2001). Because oviposition did not occur in any of the experimentally placed receptacles, mosquito distribution patterns from this method could not be analyzed. The twenty larvae found inside the home, should bring to attention the risks that are imposed by having open water receptacles. Though the larvae in my study were not identified, there is still a chance that they belong to a species capable of transmitting dis ease. In 2006, one hundred and thirty nine larvae were found in household items in Cuajiniquil (Jafari 2006). Over one hundred of the larvae belonged to Aedes , a genus with a species known to carry dengue fever. This goes to show that residents in this are a may be unaware of how to prevent larvae formation in their homes. Future studies can assess this proposal by surveying the community and their knowledge of mosquito disease transmitting mechanisms. The second part of this study analyzes adult mosquito d istribution. The highest number of mosquitoes were found in mangroves. The mangroves also contained the highest number of the dominating species, Aedes triseriatus. Out of the four genera identified, Aedes was the dominating genus. These results are import ant because this genus is known to have species that can carry numerous infections and diseases. Aedes aegpti was not identified in Cuajiniquil, meaning that public health initiatives in this area against mosquito borne illnesses may be effective. The low e st abundance of mosquitoes was found near Rio Cuajiniquil, however each mosquito sampled was identified as a different species. This suggests that it may have been the location with the most species richness if more mosquitoes were sampled. When comparing the results of my findings to the recent work of Chiverri et. al who conducted work in the La Selva Biological Station, results sh ow that the genus, Deinocerites does not appear in Heredia as it does in Cuajiniqual (2018). There are also differences bet ween the exact species of Aedes identified in these two locations. It is also important to address the fact that a yellow fever mosquito vector was found in Cha verri's study, while a malaria vector mosquito species was found in Cuajiniquil. This study als o demonstrates two medical diseases that have the potential to be transmitted if there is a host with the virus present. Anopheles pinctopennis was found near Rio Cuajiniquil. This species has been found to be a transmitter of tertian malaria (Boyd and Kit chen, 1936). Aedes triseriatus was the dominant genus identified in this study, however it was found across all four locations. According to the European Center for Disease Prevention and Control, this species is known to carry the La Crosse virus, an ill ness that causes inflammation in the brain. Future research should analyze the abundance of these two species to provide more informat ion about the risks that they pose to the community. Knowing that mosquitoes are found in all four areas of homes, forest edge, mangroves, and near Rio Cuajiniquil provides adequate information that mosquitoes are extremely prevalent in Cuajiniquil, Guanacaste, Costa Rica. My results demonstrate that there are two medical
Mosquitoes in Cuajiniquil ! Arana 6 ! diseases that may be transmitt ed from species in this area. Fumigation efforts should be considered to prevent the risk of disease outbreak occurring. ACKNOWLEDGEMENTS First and foremost, I would like to thank God for bringing me to this stage of my life. I would then like to extend huge gratitude to my pr imary advisor, Frank Joyce, who continuously gave me confidence, reassurance and endless support throughout this entire process. Thank you for challenging me and allowing me to truly learn. I also appreciate and am thankful for my secondary advisor, Emilia Triana who taught me how to identify mosquitoes and larvae. To the remaining EAP Staff: Federico Chinchilla, Sofia Arcia Flores, Andres Camacho, and Felix Salazar thank you for your support and kindness. To my Cuajninquil compaÂ–eros , my vision would have not come alive without your help. Alex, Alice, Calla, Jenna, Megan, and Michael I will always be grateful for your time and sacrifice. To the Cuajiniquil children, Sebastian, Adriana, Manuel, Mariangel, Maria and friends thank you for teaching me about za ncudos and being just as excited as I was to capture them. To my family, thank you for your love and everlasting support. LITERATURE CITED Bisset, J. A., et al. "Insecticide resistance in two Aedes aegypt i (Diptera: Culicidae) strains f rom Costa Rica." Journal of medical entomology 50.2 (2013): 352 361. Boyd, Mark F., and S. F. Kitchen. "The Comparative Susceptibility of Anopheles Quadrimaculatus, Say, and Anopheles Punctipennis, Say, to Plasmodium Vivax, Grassi and Feletti, and Plasmodium Fal ciparum, Welch1." The American Journal of Tropical Medicine and Hygiene 1.1 (1936): 67 71. Burkett Cadena, Nathan, et al. "Resting Environments of S ome Costa Rican Mosquitoes ." Journal of Vector Ecology , vol. 38, no. 1, 2013, pp. 12 Ã 19. Chaverri, Luis Gui llermo, et al. "Mosquito Species (Diptera: Culicidae) Diversity from Ovitraps in a Mesoamerican Tropical Rainforest." Journal of Medical Entomology , vol. 55, no. 3, 2018, pp. 646 Ã 653. Day, Jonathan F. "Host seeking strategies of mosquito disease vectors." Journal of the American Mosquito Control Association 21.sp1 (2005): 17 22. Horne, Nathanael. "A Possible Positive Feedback Loop for Mosquito Population Growth in Monteverde , Costa Rica." (1994): 249. Jafari, Aria. "Physical and environmental p references of mosquito larvae (Culicidae) and predation by Priapichthys panamensis in Cuajiniquil, Guanacaste." (2006): 4. Minakawa, Noboru, et al. "Anopheline mosquito survival strategies during the dry period in western Kenya." Journal of medical entom ology 38.3 (2001): 388 392. Kilpatrick, A. Marm, et al. "West Nile virus epidemics in North America are driven by shifts in mosquito feeding behavior." PLoS biology 4.4 (2006): e82. Nayar, J. K., and D. M. Sauerman Jr. "The effects of nutrition on survival and fecundity in Florida mosquitoes Part 3. Utilization of blood and sugar for fecundity." Journal of medical entomology 12.2 (1975): 220 225. APPENDIX
Mosquitoes in Cuajiniquil ! Arana 7 ! Appendix A: An example of the river water filled receptacle that was used during the first part of the study. !