(Please use this citation when referring to this work)
RODERIC F. SCHMIDT
Middlesex County Mosquito Extermination Commission, 200 Parsonage Road, Edison, NJ 08820
Abstract: County mosquito control agencies in New Jersey were polled in their methods of conducting landing rates and bite counts. Using this information and other references, guidelines are presented to create a unified approach in the use of landing rate/bite count data for mosquito control.
Introduction: In preparation for this talk on landing rates and bites counts, I conducted a survey of New Jersey mosquito control agencies and discovered that there is wide variation on how the counts are conducted. In some cases, the agencies indicated that they made no distinction between the two. This paper will attempt to distinguish the differences and make guidelines for their usage in mosquito control.
The Evolution of Bite Count Methodology: At one point in the history of New Jersey mosquito control there was no formal adult surveillance. Mosquito control agencies thought that by polling the people that lived in an area where reduction work was taking place they could determine how successful the effort was. This type of surveillance proved unreliable so the birth of adult surveillance occurred.
You will have to remember that this took place before the New Jersey light trap existed. Before the light bulb was used as an attractant, the human body was used as the substitute. This type of adult surveillance was not referred to as either a landing or bite count but as a day or night collection. The first recorded information I could find on adult surveillance was written by Dr. Headlee in 1917.
He talked of a day collecting trip to the New Jersey shore for Aedes sollicitans and I quote, "All collections were made in shrubbery or tall weeds in broad daylight. All collections were the work of two (2) collection bottles. When the total catch in five (5) minutes reached 30 the limiting factor became the length of time necessary for the bottles to kill.
For information on night adult surveillance I asked Mr. Jessie B. Leslie if he could help me and he agreed. To the best of Mr. Leslie's recollection, a night collection was twenty (20) minutes in duration. Each inspector was assigned a location, Mr. Leslie's being in Carlstadt on top of a hill. The inspector would report to his post at dusk, roll up his sleeves and wait. They would use killing tubes to capture the insects. As Mr. Leslie told me, "it was primitive but effective and as we were starting from scratch, it did help to give us the necessary information as to density and species". Change the wording a little and these descriptions could be the landing or bite counts taken last summer.
When adult surveillance came into greater use, the shortcomings and variables became apparent. They included: mosquito habits, air movements, atmospheric moisture, temperature, light intensity, precipitation, elevation, plant growth, differences in collectors (such as bodily attractiveness, manual dexterity in catching the mosquitoes and earnestness with which the mosquito employees performed their job of collecting). All of these variables still exist today yet the list comes from a paper given by Dr. Headlee in 1922 at the ninth annual meeting of the New Jersey Mosquito Extermination Association. The New Jersey light trap was invented because of the variables encountered by the early mosquito control workers, but that is another story. In summary, day collections were called landing counts and night collections were termed for bite counts. There might be an evolutionary connection.
Results of the Questionnaire: Most counties define a landing rate as an observation on the density of mosquitoes in an area with little or no concern for species present. They are concerned with the numbers that are coming to bite rather than the species composition. On the other hand, most counties use a bite count when the agency wants to have hard evidence on the number of mosquitoes coming to feed plus what species they are.
Most mosquito control agencies have an official form on which to record this information. The form has a space to record the start and finish of the count, location at which it was taken, species collected and some types of meteorological observations.
The time at which either landing rates or bite counts are conducted varies among the different agencies. Both methods were conducted during the daytime as well as evening with most of the counties taking them in the evening until slightly after sunset or until artificial light was needed.
When artificial light is necessary, a flashlight is usually used although some agencies make use of vehicle headlights. Two agencies used red filters on their flashlights; most use unfiltered light.
Most agencies use one or two people to make the counts but the team may be as high as four. The special instructions varied considerably and often conflicted from county to county. The following is a list of the instructions we received in the poll:
There was also variation regarding the duration of the counts. Most agencies take bite counts over a 5-10 min. period and record landing rates for 1 min. Some agencies, however, prefer periods that vary from 1 min. to as high as 30 min. for either technique. When mosquitoes are actually collected, most agencies identify them to species and keep the information on a special form. Many make the information available to the homeowner if the data are collected in the homeowner's yard.
Landing rate and bite count data are used for many different purposes by the mosquito control agencies that were polled. The primary use is justification for adulticiding. Other uses include: 1) Justification for water management projects, 2) Effectiveness of adulticiding, 3) Larval habitat location, 4) Vector potential of biting populations, 5) Light trap placement, 6) Improved larval surveillance and 7) A comparison of biting populations vs. light trap data.
Guidelines for Conducting Bite Counts and Landing Rates: The more I looked at the information from the questionnaire the only thing of uniformity that came out of it was how non-uniform we are as mosquito control agencies. The following guidelines are presented to eliminate variation when we conduct our landing rates and bite counts.
The term "Landing Rate" should be used when an individual records the number of mosquitoes that land on the observer over a designated period of time. We suggest that they be taken over either a I or 5 min. period. If the landing rates exceed 50 in 30 sec., the interval can be shortened to protect observers that are expected to conduct numerous counts. Landing rates may involve speciation, if desired, but they are normally employed in areas where a single, known species is the sole cause of annoyance.
The term "Bite Count" should be used when an individual captures each mosquito that comes to bite over a designated time interval for species determination. Bite counts are most useful in areas where the biting populations consist of mixed species. The same time restrictions can be employed with an upper limit of ten (10) minutes when the biting populations are extremely low.
The following guidelines apply to both landing rate collections and bite count collections:
"Kama ilivyoelezwa katika makala ya kwanza ya jarida la ""Middle East,"" Shirika la Ulinzi wa Mbu la Kaunti ya Middlesex, 200 Parsonage Road, Edison, NJ, NJ, lilijibu maswali ya wataalamu wa udhibiti wa mbu katika New Jersey kuhusu viwango vya kutua na hesabu ya kuumwa." Kwa kutumia habari hii na marejeo mengine, miongozo inapatikana ili kuunda mbinu ya umoja katika matumizi ya kiwango cha kutua na data ya hesabu ya kuumwa kwa udhibiti wa mbu. "Kupitia utafiti wa ""Uchunguzi wa Uvuvi wa New Jersey,"" tuligundua kwamba kuna tofauti kubwa katika jinsi hesabu za mbu zinavyofanywa." Katika visa fulani, mashirika hayo yalionyesha kwamba hayakufanya tofauti kati ya mambo hayo mawili. Karatasi hii itajaribu kutofautisha tofauti na kufanya miongozo kwa ajili ya matumizi yao katika udhibiti mbu. Kwa mfano, katika New Jersey, kwa mfano, katika kipindi cha udhibiti wa mbu, hakuna ufuatiliaji rasmi wa watu wazima. Mashirika ya kudhibiti mbu yalidhani kwamba kwa kuwauliza watu walioishi katika eneo ambalo kazi ya kupunguza mbu ilikuwa ikifanywa wangeweza kuamua jinsi jitihada hizo zilivyofanikiwa. Aina hii ya ufuatiliaji ilithibitika kuwa isiyoaminika kwa hivyo kuzaliwa kwa ufuatiliaji wa watu wazima kulitokea. Unapaswa kukumbuka kwamba hilo lilitukia kabla ya mtego wa taa wa New Jersey kuwepo. Kabla ya balbu ya umeme kutumiwa kama kichocheo, mwili wa binadamu ulitumiwa kama mbadala. Aina hii ya ufuatiliaji wa watu wazima haikutajwa kama ama kutua au kukata hesabu lakini kama mkusanyiko wa mchana au usiku. Taarifa ya kwanza ya kurekodiwa niliyoweza kupata juu ya ufuatiliaji wa watu wazima iliandikwa na Dk. Headley mnamo 1917. "Amesema: ""Nilikuwa nikikusanya Aedes sollicitans kwenye pwani ya New Jersey, na nilikusanya kwenye vichaka au magugu marefu wakati wa mchana." Mkusanyiko wote ulikuwa kazi ya chupa mbili (2) za ukusanyaji. Wakati jumla ya samaki katika dakika tano ilifikia 30, sababu ya kikomo ilikuwa muda unaohitajika kwa chupa kuua. Kwa habari juu ya ufuatiliaji wa watu wazima wa usiku nilimwuliza Mheshimiwa Jessie B. Leslie kama angeweza kunisaidia na alikubali. Kwa kumbukumbu bora ya Mheshimiwa Leslie, mkusanyiko wa usiku ulikuwa na muda wa dakika ishirini (20). Kila mkurugenzi alipewa eneo, Bwana Leslie akiwa katika Carlstadt juu ya kilima. Inspekta angeripoti kwenye kituo chake wakati wa giza, akifunga mikono yake na kungojea. Walitumia mirija ya kuua ili kuwakamata wadudu. "Kama vile Leslie alivyosema, ""ilikuwa ya awali lakini yenye matokeo, na kwa kuwa tulikuwa tukichukua hatua ya kwanza, ilituwezesha kupata habari muhimu kuhusu idadi ya wanyama na spishi.""" Badilisha maneno kidogo na maelezo haya yanaweza kuwa kutua au kukata hesabu kuchukuliwa majira ya joto iliyopita. Wakati uangalizi wa watu wazima ulipotumiwa zaidi, mapungufu na vigezo vilionekana waziwazi. Mifumo ya kukusanya mosquito ni pamoja na: tabia ya mosquito, harakati za hewa, unyevu wa anga, joto, mwangaza, mvua, urefu, ukuaji wa mimea, tofauti katika collectors (kama vile kuvutia mwili, dexterity manual katika kukamata mosquitoes na bidii ambayo wafanyakazi mosquitoes kufanyika kazi yao ya kukusanya). "Hata hivyo, kwa sababu ya hali hiyo, jina la ""Mbuzi"" lilitolewa na Dr. Headley katika mkutano wa mwaka wa tisa wa New Jersey Mosquito Extermination Association." Mtego wa mwanga wa New Jersey ulibuniwa kwa sababu ya mabadiliko yaliyokumbana na wafanyikazi wa mapema wa kudhibiti mbu, lakini hiyo ni hadithi nyingine. Kwa muhtasari, makusanyo ya siku yaliitwa hesabu za kutua na makusanyo ya usiku yaliitwa hesabu za kuumwa. Huenda kukawa na uhusiano wa mageuzi. Kwa mujibu wa ripoti hiyo, idadi ya mbu katika eneo la nchi hiyo ni ya chini sana na ni ya chini sana kwa aina zote za mbu. Wao huhangaikia idadi ya wanyama wanaokuja kuumwa badala ya aina ya wanyama wanaowekwa. Kwa upande mwingine, kaunti nyingi hutumia hesabu ya kuumwa wakati shirika linataka kuwa na ushahidi thabiti juu ya idadi ya mbu wanaokuja kula pamoja na spishi gani. Mashirika mengi ya kudhibiti mbu yana fomu rasmi ya kurekodi habari hiyo. Fomu hiyo ina nafasi ya kurekodi mwanzo na mwisho wa hesabu, mahali ambapo ilichukuliwa, spishi zilizokusanywa na aina fulani za uchunguzi wa hali ya hewa. Wakati ambapo ama viwango vya kutua au kuhesabu kuumwa hufanywa hutofautiana kati ya mashirika tofauti. Utaratibu huo ulifanywa wakati wa mchana na jioni, na kaunti nyingi zilitumia njia hiyo jioni hadi baada ya jua kutua au hadi mwanga wa bandia ulipohitajika. Wakati mwanga bandia ni muhimu, flashlight ni kawaida kutumika ingawa baadhi ya mashirika kufanya matumizi ya taa za mbele za gari. Mashirika mawili yalitumia vichungi vyekundu kwenye taa zao za mkononi; mengi hutumia nuru isiyochujwa. Mashirika mengi hutumia mtu mmoja au wawili kufanya hesabu lakini timu inaweza kuwa juu kama nne. Maagizo ya pekee yalitofautiana sana na mara nyingi yalipingana kutoka kaunti moja hadi nyingine. "Hii ni orodha ya maagizo tuliyopokea katika uchaguzi: ""Kulikuwa na tofauti kuhusu muda wa kuhesabu." Wakala wa kawaida wa kupima huchukua dakika 5-10 kwa kila mlo. Wakati huo huo, ndege hiyo ilirekodi viwango vya kutua kwa dakika moja. Hata hivyo, baadhi ya mashirika hupendelea vipindi vinavyotofautiana kutoka dakika moja hadi tano. kwa kiwango cha juu kama 30 min. kwa ajili ya mbinu yoyote. Wakati mbu zinakusanywa, mashirika mengi huwatambulisha kwa spishi na kuweka habari hiyo kwenye fomu ya pekee. Wengi hufanya habari iweze kupatikana kwa mmiliki wa nyumba ikiwa data hukusanywa katika uwanja wa mmiliki wa nyumba. Takwimu za kiwango cha kutua na hesabu ya kuumwa hutumiwa kwa madhumuni mengi tofauti na mashirika ya kudhibiti mbu yaliyopigwa kura. Matumizi yake ya msingi ni kuhalalisha uzinzi. "Kama vile, ""Utekelezaji wa miradi ya usimamizi wa maji, ufanisi wa adulticide, eneo la makazi ya larval, uwezo wa vector wa idadi ya watu, uwekaji wa mtego wa mwanga, kuboresha ufuatiliaji wa larval na kulinganisha idadi ya watu na data ya mtego wa mwanga.""" """Miongozo ya kufanya hesabu ya kuumwa na viwango vya kutua: Kadiri nilivyoangalia habari kutoka kwa maswali, jambo pekee la usawa ambalo lilitoka ni jinsi sisi sio sawa kama mashirika ya udhibiti wa mbu." Miongozo ifuatayo inapatikana ili kuondoa tofauti wakati tunafanya viwango vyetu vya kutua na hesabu za kuumwa. "Neno ""kiwango cha kutua"" linapaswa kutumiwa wakati mtu anapoandika idadi ya mbu wanaotua juu ya mtazamaji kwa kipindi maalum cha wakati." Tunapendekeza kwamba ufanye hivyo kwa dakika 1 au 5 kipindi. Ikiwa viwango vya kutua vinazidi 50 katika sekunde 30, muda huo unaweza kufupishwa ili kuwalinda watazamaji ambao wanatarajiwa kufanya hesabu nyingi. Viwango vya kutua vinaweza kuhusisha spishi, ikiwa inahitajika, lakini kwa kawaida hutumiwa katika maeneo ambapo spishi moja inayojulikana ni sababu pekee ya usumbufu. "Kuhusu ""kuchoma,"" ni muhimu kutambua kwamba kila mbu anayekamata ni mnyama wa aina moja, na kila mnyama anayekamata ni mnyama wa aina moja." Hesabu za kuumwa ni muhimu zaidi katika maeneo ambapo idadi ya watu wanaokula hufanyizwa na spishi mchanganyiko. Vipingamizi vya wakati sawa vinaweza kutumiwa na kikomo cha juu cha dakika kumi (10) wakati idadi ya kuumwa ni ya chini sana. Miongozo ifuatayo inatumika kwa wote kukusanya kiwango cha kutua na kukusanya hesabu ya kuumwa: