VANHEUANG PHOMMADEECHACK

[VANHEUANG PHOMMADEECHACK]

Hello everyone! I’m Vanheuang Phommadeechack. Student ID: 6436660
I will answer and discuss questions below: How epidemiology of vectors improve vector control? (Give example and discuss)

Epidemiology is the study of diseases to investigate how, when and why the disease is occured. The information can be used to control the spread of the disease and prevent future outbreaks. In terms of entomology, epidemiology of vectors also important for prevention and vector controlling programs and understand vector capacity, the dynamic of vector population and disease. There are several factors that affect the current status of vector-borne diseases such as the Environmental factor, human, meteorological (temperature, humidity, visibility, and wind speed), seasonal and climate change.

For example the study that conducted by Tamaree et all (2021), they study a spatio-temporal analysis of scrub typhus and murine typhus in Laos, which we know these diseases are causes of febrile illness. Scrub typhus (ST) is caused by Orientia tsutsugamushi, transmitted by the bite of chiggers mites. Murine typhus (MT) is caused by Rickettsia typhi and is transmitted by fleas. Both diseases are neglected with under-estimated burdens on health and little is known about the temporal dynamics of these diseases, and the influence of climatic and environmental factors

In this study, they investigated individual-level demographic and behavioral characteristics of patients; spatial and temporal distributions; meteorological correlates of the temporal patterns; and environmental and geographic correlates of the spatiotemporal distributions.

The result shows that ST was highly occur during the wet season between July-September compared to the dry season whilst MT peaked in the dry season. ST incidence to fluctuations in relative humidity whereas MT was linked to variation in temperature. In addition, patients with ST infection were more likely to come from villages with higher levels of surface flooding with the patient-related or contact with the rice field.

The data suggest that the risk of disease will be increase as cities expand. They also suggested that the incidence and spatial distribution of both MT and ST will increase. According to the information of the distribution or the epidemiology of MT and ST, we will know the time period of disease outbreak and know the dynamic of the disease and vector … in Vientiane, which very helpful for using as the reference information for disease prevention and vector controlling program to reduce the risk of disease transmission.

Reference :Roberts T et all. A spatio-temporal analysis of scrub typhus and murine typhus in Laos; implications from changing landscapes and climate. PLoS Negl Trop Dis. 2021 Aug 25. doi: 10.1371/journal.pntd.0009685.

Thank you very much.

[VANHEUANG PHOMMADEECHACK]

Hello everyone!
Please find my opinion as below:
1. I have sent pictures of the mosquito ovaries to Ajan via email.
The mosquito ovary can be used to evaluate the age of the mosquito and also can be used to determine whether this female mosquito has laid eggs before or not. We can dissect the ovary of the mosquito (fed or non-feeding) under a stereomicroscope by using minute needles. I start with anesthetizing a female mosquito by using Ether and then remove their legs and wing to make sure that it can’t move. Put mosquito on the prepared slide with normal saline and prepare another slide for transferring the ovary. Separate mosquito in to 2 part head+thorax and abdomen using minute needle, lay the needle across the 7th abdomen segment and slowly detach the terminalia, transfer ovaries to prepared slide, cover by cover slip, leave it dry and observe under the microscope.
The term Parity is the term that use to determine the age of wildlife including mosquitoes. There are parous and nulliparous that describe the parity status of the female mosquito as below:
1.1 Parous means the female mosquito that has taken the blood meal and has laid egg before. We can see that the tracheole is distributed. Sometimes, we also can see the egg-containing in the ovaries.
1.2 Nulliparous is the term that us to describe the female mosquitoes that never lay egg or feeding. We can see that the tracheole is tightly coiled call “skein” show inside the circle.

2. The termination of blood source and mosquito parity rate are important in role of vector capacity, because we will know the host preference, host-feeding pattern and proportion, and we also know the longevity of the mosquitoes from age determination of mosquito to apply in the monitoring of disease transmission and vector control.
– The method for blood source determination can be done by precipitin test, ELISA, multiplex PCR or DNA barcode, Microsatellites and Mass spectrometry.
– The method for age determination can be done by examining the morphology of ovaries or the structure of the tracheal system. Each of dilatation represents one gonotrophic cycle, so we can use this tool for estimating the age of the mosquito.
– Application of blood determination and mosquito parity rate is for surveillance and monitoring of vector capacity.
The application that use for age determination can be done by the multiplication between Number dialatation and days of gonotrophic cycle (Age grading= Number dialatation x days of gonotrophic cycle).

Thank you very much and happy to hear feedback and discuss with ajan and friends.

Cheers!
Vanheuang Phommadeechack. Student ID: 6436660

[VANHEUANG PHOMMADEECHACK]

Hello everyone, I am Mr. Vanheuang Phommadeechack Student ID: 6436660

This is an interesting topic for me in terms of medical entomology and epidemiology. let’s see my opinion below:
1. For routine work in vector surveillance of malaria, i think the objective to conduct this task is for planning for vector control program and for early warning of disease outbreaks in the specific area and for evaluating the effect of vector control.
– In my opinion, we should start with planning first to design the study and select the appropriate method for sampling like cluster sampling, systematic sampling, random sampling.
– After that, we will plan for the collection technique and the form such as data collection form, data record form, plan to record data in “Excel sheet”, then plan for the equipment to use for sample collection, and plan for mapping (where to collect the sample), set the schedule and timeline to collect the sample.
– Choose the suitable type of collection method like adult collection by using resting collection, biting collection and trapping collection.
– Record and preserve the sample in appropriate way for further investigation which based on the purpose of study then transport the sample to the laboratory, for example keep in cryotube or Eppendorf tube with cilica bead.
– Then we will select type of vector survey, for example we can use preliminary survey for short term, regular or trend observation for monthly or based on season, and spot check. This can be used to evaluate the effect of vector control.
– Analysis of the data from lab results and report the result of the surveillance including the description of the study, worksheet report, discussion, comment, interpretation and conclusion.

2. For the situation of malaria outbreak in Thai-Myanmar border in Tak province, If we would like to take part for the identification of disease outbreak or vector surveillance, I think we should proceed as following process.
– Set the objective that can answer or can solved the problem. For the objective of vector surveillance in Thai-Myanmar border in Tak province is to identify the cause of disease outbreak, for species identification of mosquitos that caused the disease outbreak in that area, for vector controlling, for early warning of malaria outbreak in that area and to evaluate of vector control.
– Planning:
For the study design I think Cross-sectional study because this is the most appropriate to collect the sample in the specific period for vector surveillance. To collect the sample, I choose the systematic sampling method to collect the mosquito or collect the sample nearing malaria case report areas to get representative of sample in that area, writing study protocol calculate the sample size.
– Program activities: setting the timeline and schedule to collect the sample, listing the activities to be done in every day
– Methods:
. Equipment and tools: preparing the equipment that will be use in sample collection and preparing the data colleting form.

. Vector collecting technique: I will use trapping method to collect the adult anopheles mosquito such as light trapping, BG trapping and set the trap in early evening and leave it overnight with trap labeling and mapping record, then collect the trap in the morning of next following day.
. Sample preservation: sample will preserve in silica bead with labeling or sample coding and record in excel sheet.
. Sample transportation: sample will pack in a primary and second container with icepack and sealed before transport to the laboratory
. Laboratory investigation: Morphology, molecular identification for species (COI gene) and for malaria detection in mosquito (qPCR for malaria detection).
– Analysis: Data of sample and laboratory test results will be recorded in the excel sheet, then will summarize the data based on identified species of morphology and molecular, and analyze the data according to molecular laboratory results of malaria detection in mosquitoes using qPCR.
– Reports: the result of the study will be reported by data summary with the conclusion of the result, the description of the study, discussion, comment, interpretation of the data analysis and conclusion of the study.

Happy discuss and hear comments and feedback from Ajan and friends.

[VANHEUANG PHOMMADEECHACK]

TMEN513 Lab exam: Cockroaches and bugs
Mr. Vanheuang Phommadeechack ID:6436660

Question1: Please describe how you identify the cockroaches (selecting at least two species)
Answers: We can use morphology characteristics to describe cockroaches species as some species below:
– Periplaneta americana (American cockroach): it is a group of large size cockroaches. They have wings that covers all the abdomen and there are some pale areas on the pronotum. Both male and female cercus, last segment is twice as long as wild, whilst in male there are stylets presented.
– Periplaneta australasiae (Australian cockroach): it is also a group of large size cockroaches and the morphology is quite the same with American cockroach but the pronotum is ringed with similar coloration, one special characteristic of Australian cockroach is that there are pale lateral markings on the upper edges of tegmina wings on both sides.
– Supella longipalpa (Brown-banded cockroach): it is a group of small size cockroaches, there are two transverse dark bands on wings. In females, wings are shorter than abdomen. Whereas, in male wings are longer than abdomen

Question2: What is the difference between genus Triatoma and Rhodnius?
Answers: Triatoma spp. and Rhodnius spp. are tiatomine bugs (kissing bugs) in the family of Reduviidae and subfamily of Triatominea. It can be the vector of Trypanosoma cruzi, which is the agent that causeed Chagas’ disease. The difference between genus Triatoma and Rhodnius genus is piercing-sucking mouthpart position, as we can see that Triatoma specie the antennae arise from side of head at the middle in the between eye and the tip, but in the Rhodnius spp. antennae arise from sides of the head at the anterior end. The rest other morphology characteristics of both Triatoma and Rhodnius is quite the same, it has a cone-shaped head on a narrow neck and an abdomen that is widened in the middle, the front wings are hemelytra type.

Note: The scientific name cannot write in italic in the comment.

[VANHEUANG PHOMMADEECHACK]

TMEN513 lab exam Tick and mites
Student name: Mr. Vanheuang Phommadeechack ID: 6436660

Question 1: What is the respiratory organ of the suborder Astigmata? How do they breathe?
Answers: The suborder Astigmata includes the family Sarcoptidae (itch mite) and family Pyroglyphidae (house dust mites). In general, they breathe by means of tracheae, or air tubes, but in many species, respiration takes place directly through the skin.

Question 2: What is the difference between hard tick and soft tick? How you differentiate between male and female of hard tick?
Answers:
The difference between Hard tick and soft tick are: Hard tick has the hard plate on the back of the body called scutum or dorsal plate and mouthparts project out in front of the body call false head, hard ticks have eyes on the scutum of dorsal part. For soft tick, mouth part is underneath the body, no eyes and no hard plate on the body. Its body is flexible, tough, bulbous bodies that cover the mouthparts and most of the legs
Differentiation between male and female hard tick:
The characteristic of adult hard tick that use to differentiate male and female hard tick is scutum, the scutum of male hard tick is cover the whole body but for the scutum of female hard tick is cover only 1/3 part of the body. For other characteristics, both male and female are quite similar such as both male and female have 4 pairs of legs (8 legs), spiracle located posterior to the base of the fourth pair of legs and the mouth part protruding anteriorly.

Question 3: Please describe how you characterize the mites (at least two groups)
Answers:
Mites are the arthropod that classified in class Aracnida and subclass Acari. It can cause the disease (house dust mite, scabies mite, etc) and it also can be the vector to transmit the disease (chigger mites). I will describe some groups as below
– Characteristic of house dust mite (Dermatophagoides spp.): the size is very small, cuticle finely or coarsely wrinkled, the genital organ is located between last two pairs of legs, found anus in ventral. Reverse y or v shape of valva (female), in male there is genital opening and we can see that v shave of the sexual organ of male is smaller than female.
– Characteristic of Trombiculid mite (Chigger mite): Chigger mite is the vector of scrub typhus (caused by Orientia tsutsugamushi), it has 3 pair of legs in the larval stage, palpi have 5 segments, there are two segment in the chelicerae and we can found the scutum bears in the dorsal.

Note: The scientific name cannot write in italic in the comment.

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