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| The officers and entomologists working as "mosquito surgeons" quietly serve the scientific cause. |
Mosquito dissection - a technique to determine the role of mosquitoes in transmitting malaria (Part 1)
Surgeries on humans, livestock, and poultry are commonly discussed, but within the specialized field of medical entomology, an often-employed technique in regions where malaria is prevalent or during outbreaks involves mosquito dissection. This practice aims to study various physiological traits of mosquitoes, such as determining their mating status, parity status, frequency of egg laying, identifying different developmental stages of mosquito eggs, and assessing the mosquitoes' role in disease transmission. This examination involves scrutinizing the mosquito's stomach wall for the presence of oocysts and the mosquito's salivary glands for sporozoites of parasites, acquired after feeding on the blood of humans or animals. Understanding these fundamental aspects helps identify dangerous mosquito species, their peak activity periods, and aids in devising effective malaria prevention and control measures. The Anopheles Mosquito: A Vector in Malaria Transmission Malaria, a disease transmitted by mosquitoes, is widely known. Viet Nam hosts 59 species of Anopheles mosquitoes, with 15 species identified as primary, secondary, or suspected vectors of malaria. The primary vectors include An. minimus, found in national mountainous forests; An. dirus, prevalent in forested mountainous regions from latitude 20o north to the south; and An. sundaicus, located in coastal breakish water areas of the Mekong Delta. Female Anopheles mosquitoes exclusively carry and transmit malaria. Identification of an Anopheles species as a malaria vector primarily hinges on the presence of sporozoites within the mosquito's salivary glands. Detection methods involve microscopic dissection to locate sporozoites or employing the Enzyme-linked immunosorbent assay (ELISA) technique to identify circumsporozoite protein within the mosquito's body. While mosquito dissection is a traditional and accessible technique applicable in various facilities, ELISA demands more sophisticated equipment and controlled conditions. Dissecting mosquitoes to determine mating status The determination involves a straightforward method that entails dissecting female mosquitoes to examine the spermatheca located in the 8th abdominal segment. This examination aims to observe whether there are sperm from a male mosquito. The spermatheca, visible through the abdominal membrane, appears as a small, dark brown spherical sac, resembling a golf ball with an opening. To observe the spermatheca, gently pulling the terminal part of the 9th abdominal segment reveals it adjacent to the Malpighian tubules, ovaries, and digestive organs. Separating and observing it under appropriate magnification helps determine if the female mosquito has mated or not. While this technique is uncomplicated and relatively inexpensive in terms of the required tools, it can only be performed on live or freshly deceased female mosquitoes.  Anatomy of an adult mosquito Dissecting mosquitoes to assess egg laying frequency Determining whether a female mosquito has laid eggs involves a dissection technique that exposes the hungry female mosquito's ovaries, specifically examining the tracheoles. In newly emerged female mosquitoes, the tracheolar tubes initially form tightly coiled clusters. However, after the first blood meal and the commencement of egg development, these tubes extend and no longer coil back. This observable change helps differentiate between mosquitoes that have laid eggs and those that have not. 
Source: wikipedia.org This distinction is crucial for assessing the proportion of parous mosquitoes, thereby indicating their reproductive cycle. This information is pivotal in estimating the potential survival capabilities and average lifespan of mosquitoes. Understanding their reproductive patterns provides valuable insights into their life expectancy.  Wading through streams, climbing over hills to catch mosquitoes and larvae According to the World Health Organization (WHO), the survival rate of mosquitoes is a crucial mathematical measure determining the potential lifespan of a female Anopheles mosquito. This rate holds immense significance in terms of malaria transmission, influencing whether an Anopheles mosquito lives long enough to complete a sporozoite cycle within its system. Moreover, the mosquito's survival capability post-infection with malaria parasites in its salivary glands directly impacts the frequency of potential malaria transmissions to hosts. This factor relies heavily on how long the infected mosquito can survive and continue feeding on hosts. Observing the exterior of an adult mosquito Head | Location of the eyes and brain, and where the antennae attach. | Proboscis | Tube-like mouth part used to suck up fluids. In females, this is strong enough that it can pierce skin. | Antenna | Movable segmented feather-like feeler that detects chemicals like carbon dioxide and air currents. | Palp | A sensory organ that can detect odors and can feel objects. | Compound Eye | Eyes made of many light detectors called ommatidia. | Occiput | The back of the head. | Thorax | Midsection where the (6) legs and (2) wings attach. | Antepronotum | A protective plate that sits on top of the front of the thorax. | Scutum | The large front section of the thorax. | Scutellum | The middle section of the thorax. | Postnotum | The end of the thorax, which also holds the septum that separates the thorax and the abdomen. | Halter | An organ that helps mosquitoes to steer while they fly. | Abdomen | The hind part of the mosquito, where most of digestion, eliminating waste, and reproduction occurs. | Abdominal segments | Sections of the abdomen. Each segment has a top and a bottom that are separated, allowing the abdomen to expand with a meal or with eggs. | Cercus | A projection from the end of the abdomen that is involved in mating and in egg-laying. | Tarsomeres | Moveable parts of the end of the leg. | Tarsus | The last segment of the leg and what touches the walking surface. | Tibia | Fourth segment of an insect leg; the tibia of the hind leg holds the pollen basket, where pollen is carried. | Femur | Third segment of an insect leg. | Foreleg | Leg located closest to the head. | Mid Leg | Leg located between the foreleg and hind leg. | Hind Leg | Leg farthest from the head. | Wing | Flat projections from the body that are used in flying. | Longitudinal Veins | Thickenings in the wing that lie along the long axis of the wing. | Crossveins | Thickenings in the wing that lie along the short axis of the wing. |
Labeled illustration of the external anatomy of a mosquito. Image modified from LadyofHats via Wikimedia Commons.
Examining the interior of an adult female mosquito
Proboscis | Tube-like mouth part used to suck up fluids. In females, this is strong enough that it can pierce skin. | Salivary glands | Glands that make saliva. When saliva enters a mosquito bite, it helps make blood flow from the host, it numbs the skin, and it may pass along parasites, viruses, or bacteria that cause disease. | Dorsal diverticulum | A pouch in the anterior portion of the digestive system that is involved in sugar digestion. | Anterior midgut junction | A part of the anterior digestive system that helps meals to be processed in the correct part of the system. | Crop | A sac that stores sugary meals like nectar. | Stomach | A part of the posterior digestive system. Blood meals are sent directly to the stomach to be digested. | Ovaries | A part of the reproductive system, where eggs develop and are stored. | Malpighian tubule | An organ involved in the regulation of body water and hydration, as well as in getting rid of waste. | Anus | The end of the digestive tract, where wastes are removed from the body. |
 Labeled illustration of the internal anatomy of a female mosquito.
Illustration by Karolina Mikolajczyk.
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