Category Archives: 12th March

Nina Paulic


Establishing of the dispersion capacity of Simulium ornatum Meigen, 1818 (complex) larve by application of methylen blue vital dye

Nina Pualić, Aleksandra Ignjatović Ćupina, Marija Zgomba, Dušan Petrić
University of Novi Sad, Faculty of Agriculture, Laboratory for Medical and Veterinary Entomology,T.D.Obradovića 8, 21000
Novi Sad, Serbia

Identification of the dispersion capacity of S. ornatum late instar larvae, by artificial positioning in the upstream uninhabited sections of the stream, distant from typical breeding zones was the main
objective of this study. Further more, the convenience of methylen blue vital marker application as a suitable tool in biological studies of black flies in natural environmental conditions was tested.
Larval marking was performed in methylen blue aqueous solution 25 mg/l and 45 minutes exposition. High portion of visually detectible dyed larvae (about 90%) was recorded, no mortality and high persistence of the dye in the larval body all over the 15 days period.
Tendency of dispersion and successive inhabitation of downstream sections at increasing distances was expressed in majority of larvae (99,33%). The increase of distances covered in function of time
was recorded, starting from 17 m to 93 m after 1 and 15 days, respectively.

Filiz Gunay

Variation in the productivity (Ro), morphology and age specific mortality in Culex quinquefasciatus (Diptera: Culicidae) samples reared at different constant temperatures

Filiz Günay, Ergi Deniz Özsoy and Bulent Alten Hacettepe University Faculty of Science Department of Biology 06800 Beytepe-Ankara-TURKEY

Over the last six years, several vector-borne, parasitic or zoonotic diseases have emerged, re-emerged or spread in the European territory, especially in southern Europe, with major health, ecological, socioeconomical and environmental consequences. Most of these outbreaks are linked to global and local changes
as ecosystems, habitats, rangeland disturbances, mostly instabilities resulting of climatic changes or growth in human populations and their activities.
As we know that the earth’s climate is in a warming phase, a part of which may be due to human activities.
Both local and global changes may independently or in combination have a negative impact on human and animal health by favouring the spread of vector-borne diseases. Recent experiences with West Nile Virus show how diseases may appear in one continent, be transferred to other continents and become widespread
within the space of a very few months. Many of vector-borne diseases are not only dependent upon carriers that are themselves very sensitive to their environment, the local climate and weather, but also have some of the greatest capacities for rapid increase over short periods of time and for rapid evolutionary responses to
new situations.
It is well known that one of the most important factors affecting the biology and morphology of vectors is temperature. Hypothesis is that populations of Cx. quinquefasciatus rearing under different temperature regimes show subtle variations in reproductivity, morphology and also age specific mortality. A purpose of
this work is to evaluate the dissimilarities among cohorts reared at different five constant temperatures (15 oC, 20 oC, 23 oC, 27 oC and 30 oC) using geometric morphometrics and demographic techniques.
Maximum likelihood estimations of the rate of increase in age specific mortality (the b parameter from Gompertz function) were calculated in Culex quinquefasciatus samples reared at different temperatures.
Between temperature comparisons to assess if significant differences in age specific mortality occured rearing the samples at different temperatures were performed via a likelihood ratio test. In that way, variation in age specific mortality in response to temperature was defined in terms of a reaction norm after one
generation of rearing.
Rearing temperatures affected egg, larval and pupal formation and also the lenght of the developmental period from egg to imago. Furthermore, when temperature increased adult longevity decreased for both sexes. While significant differences could be demonstrated among cohorts for predictive parameters such as
net reproductive rate, Ro, and generation time, Tc, no significant differences among the cohorts were found in terms of intrinsic rate of increase, rm, finite rate of increase,, birth (b) and date (d) rates. As we know, the net reproductive rate (Ro), integrates several important variables, and is indicative for the absence (if<1) or
presence (if>1) of potential spread of disease. Therefore, Ro values and the productivity of all cohorts in different temperatures were determined as “presence (if>1)”. Almost 20 parameters in all life stages were used as phsiological variables and these operational taxonomic units were analyzed using Principal
Component Analysis (PCA).
Wing shape was analyzed using 22 wing landmarks following mosquito rearing at constant temperatures.
Geometric morphometric analysis showed that variables in wing shape and size were statistically correlated with rearing temperatures in both sexes..

Christian Engelbrecht

Continuous trapping of adult Asian tiger mosquitoes (Aedes albopictus) with BGSentinel traps reduced the human landing rate and density indices in an urban environment in Cesena, Italy.

Ch. Engelbrecht1, C. Venturelli2, A. Rose3,1, M.Geier3,1
1 University of Regensburg, Regensburg, Germany
2 Dipartimento di Sanità Pubblica, Cesena, Italy
3 Biogents AG, Regensburg, Germany

Background and Objectives:
Mosquito density, longevity and the daily survival probability of mosquitoes are important factors for diseas transmission in vector-borne diseases such as Chikungunya or Dengue fever.
Conventional strategies to control the main vectors of these diseases (Aedes aegypti, syn. Stegomyia aegypti and Ae. albopictus, syn. St. albopicta) and thus to reduce the risk of disease transmission are the reduction of breeding sites and the application of insecticides.
Additional methods that are currently being tested include the release of sterile males and the continuous application of highly efficient mosquito traps. This strategy seems to be especially promising for Aedes aegypti and Ae. albopicus because of their strong adaptation to the urban environment and their limited flight
range.
The objectives of the study presented here was (1) to measure the impact of BG-Sentinel mosquito traps on local Ae. albopictus populations in an urban environment and (2) to compare the standard surveillance method using ovitraps to an adult mosquito monitoring using the BG-Sentinel mosquito traps.
Material and Methods:
The study was conducted during the summer of 2008 in Cesena, Province Forli-Cesena, Emilia Romagna,
Italy. Six clusters with similar urban, geographic and climatic conditions, and population densities for Ae.
albopictus were selected.
Three clusters received treatment with eight BG-Sentinel traps each (intervention), three clusters served as acontrol without adult mosquito traps.
Monitoring was conducted in each cluster by (1) using two ovitraps per cluster, (2) placing one (additional) BG-Sentinel as an adult monitoring trap in intervals of two to five days in every cluster, and (3) by the determination of the human landing rates once per week at the beginning of the study and twice per week later, when mosquito density increased. Captured mosquitoes were collected for later examination.
Eggs in ovitraps were counted in weekly intervals. Mosquitoes collected in the BG-Sentinel traps and in the human bait collections were all determined to species, sexed and counted. Females were dissected to determine their parity by the Detinovas tracheolation method.
Results:
In all parameters measured (human landing rate, parous rate, eggs per week), a clear difference between treatment and control areas was observed. In the clusters with the BG-Sentinel traps, the biting rate of Aedes albopictus was reduced by up to 80%, the density of adult Asian tiger mosquitoes was reduced up to 70%.
The daily survival probability, indirectly measured by the parous rate, was reduced in the treatment areas and the amount of eggs per ovitrap and week was lower in the treatment areas, compared to the control areas (reduction by up to 60%).

Somwang Kurusarttra

Identification of the potential effect of climate change on Dengue epidemic using spatial analysis in Chachoengasao province, Thailand

Somwang Kurusarttra1, Kanchana Nakhapakorn1 and Pattamaporn Kittiyapong2
1Industrial Ecology and Environment Program, Faculty of Environment and Resource Studies, Mahidol University, Nakhon
Pathom 73170, Thailand
2Center for Vectors and Vector-borne Diseases and Department of Biology, Faculty of Science, Mahidol University, Rama 6
Road, Bangkok, 10400, Thailand;

Dengue is a mosquito-borne viral infection causing a constant and serious risk to most tropical regions. As the countries become more developed and environmental transformed from rural to urban, the human population inexorable growth will change global patterns of the disease and mortality. Furthermore, changes in climate pattern phenomenon are thought to be a major contributing factor. Our aim was to indentify the potential effects of climate change on human
health, and in particular, on the incidence of vector-borne diseases. We studied among 11 districts both rural and urban sites in Chachoengsao province, Thailand from 1999 to 2007. Geographic
Information Systems (GIS) has been used to links between georeferenced factors including medical records, demographic data, and climatic data. Using multivariate regression analysis and spatialtemporal modelling, four classes of risk categories have been identified. The nearest neighbourhood method has been allowed to generate a spatial risk map. Dengue incidences in case numbers were significantly associated with climatic variables. The two most significant ones were mean minimum 2-weekly temperatures at t-1 (n = 2530, r2 = 0.245, P = 0.001) and total 2-weekly rainfall during t-2 (n = 2530, r2 = 0.137, P = 0.001). All variables, when entered into the same regression model by stepwise method, together evaluated 66.1% of the total variation in case numbers. At a small temporal scale, we assumed that the changes of land use/cover would not change much. However the predicted regression model implied that dengue epidemics were likely to associate with urbanization and industrialization. Not only they are a suitable ecological niche of denguemosquitoes in term of breeding sites and living habitats, but also urban and industrial increasing effected on the global warming directly. In summary, this research makes advances in dengue
research using GIS spatial analysis for planning prevention and control programs.

Cagasan Karacaoglu

The Use of GIS Tools in Vector Control Programs; Management and Scientific Research

Caglar S.S. and C. Karacaoglu Ç. KARACAOGLU
Hacettepe University Science Faculty Biology Department (ESRL), 06800 Beytepe, Ankara-Turkey

The GIS tools are being widely used in vector control programs. The benefits of these tools can be considered in two different aspects. One of their important role is the planning and management of
vector control programs. Another important role is more scientific that they provide some modelling oppurtinities and information on environment, vectors and parasites, diseases, etc.
Vector control programs are being done in urban, rural, touristic and many other areas all over the world, in different scales. The GIS tools are practical in managing this programs such as online tracking of staff working on field, determining the systematical sampling points, breeding sites, type and amount of insecticides used. By using the data collected and processed in GIS, future planning, predictions and decision making is more effective and easy.
Vectorial diseases can cause epidemics. In both presence and absence of vectorial diseases, if there is a vector than there is always a risk. By using remote sensing and GIS, environmental data,
entomological data, social data and many others can be converted into databases and digitally referenced data. By processing this data, distirbution maps of vectors, diseases risk maps, low and high resolution enviromental maps such as digital elevation, land use, climate maps can be created.
If we go one step further by using this GIS data some simulations with different environmental conditions can be tested for vectorial diseases epidemics.

Emma Orefuwa

The Chikungunya outbreak in the Seychelles: implications for vector control

Emma OREFUWA – Kings College, the University of London, London, UK,

The recent Chikungunya outbreak that swept across the Indian Ocean in 2005-2006 was of unprecedented magnitude. This arbovirus reached the small Indian Ocean Islands of the Seychelles
in July 2005, resulting in a two wave epidemic, totalling 9221 suspected cases, with a peak of 3832 cases in February 2006 and an overall estimated attack rate of 11% (cases from July 05-Oct 07)
The presumed vector of this incapacitating disease among the Islands affected was the container breeding mosquito, Ae. albopictus. To more fully understand the timing and development of the epidemic, an epidemiological profile of notified cases was constructed. The highest number of cases was found in the 15-44 age category which reported 13% of cases. A significant difference
was found in the number of cases reported by women compared to men ( χ2=134.106(1), p<0.0005).
With the backdrop of a high incidence of Chikungunya in Seychelles, Mahe, an ovitrap based survey was carried out for a duration of five weeks, from the 29th August to 6th Oct 2008 in residential and communal areas to study the geographical distribution and abundance of Aedes species during the Winter season.
Ovitrap surveillance was conducted for 5 weeks, conventional ovitraps were placed outside randomly selected houses and communal areas to collect outdoor breeding Aedes mosquitoes. It
was found that Aedes albopictus was the most abundant Aedes species even though a small percentage of Culex quinquesfasciatus was found to breed simultaneously in the same ovitrap.
Aedes aegypti was not found. The results from this survey indicate that the dominant mosquito species is Aedes albopictus, and that during the winter season, there are elevated levels of egg
laying. These findings indicate that monitoring and surveillance initiatives need to be ongoing to identify any risks of any future disease outbreaks that can be transmitted by the Asian ‘tiger’
mosquito.

 

Andreas Krueger

Tabanids and their medical importance

Andreas Krueger
German Armed Forces – Hospital Hamburg, Dept. Tropical Medicine at the Bernhard Nocht Institute for Tropical Medicine, Labgroup Medical Entomology. Bernhard-Nocht Str. 74, 20359 Hamburg, Germany

Tabanids (clegs, horse flies, deer flies) belong in the order Diptera to the “low” infraorder Tabanomorpha and are represented with over 3500 species worldwide, predominantly in the tropics.
Most of the 160 or so European species are confined to the Mediterranean area. Only the females feed blood on mammals including humans. They are usually diurnal and exophilic as well as
exophagous. They develop in (semi-)aquatic or terrestrial habitats. The optical remote perception of the host is steered by large, dark, heat-emitting objects (also cars!). Tabanids are good and fast
fliers, and a potential host is pursued actively by them.
Adult Tabanus species can be larger than 2 cm. The eyes of many tabanids have a species-specific, brightly coloured pattern of spots or stripes. For Chrysops species dark-brownish wing patterns are
characteristic, while in Haematopota species the wings are greyishly mottled and typically kept roof-like over the abdomen. In particular, the clearly segmented antennae distinguish tabanids from
“higher” flies. The mouthparts superficially resemble the sponging labella of the cyclorrhaph flies.
However, they accommodate stylet-like mandibles and laciniae for piercing the host skin, which leads straight to their medical and economic importance: on one hand the robust proboscis causes
quite painful bites and leaves, on the other hand, relatively large, after-bleeding wounds. These can attract other flies and be thus entrance gates for various secondary infections. In addition, the saliva may cause toxic effects. A massive nuisance of domestic animals can lead to growth inhibition and
reduced milk production. Of special interest is the role of tabanids in the cyclic or mechanical transmission of pathogens to humans and animals. Some Chrysops spp. act as obligatory vectors of
the filaria Loa loa (Nematoda: Spirurida, Onchocercidae), the causative agent of human loiasis disease in Central Africa, where approx. 10 million humans are infected. By migrating of the adult
female worms in the connective tissue (hence the German name „Wanderfilarie“) it comes to swelling („Calabar“- or „Cameroon swelling“) as well as to provoking of the eyes, if the worm
moves under the conjunctiva.
Experimental data suggest the possibility of the mechanical transmission of numerous pathogens,
but the situation in the field is widely unclear. Due to the specific behaviour of tabanids, i) short time feeder (at least Tabanus spp.), ii) causing after-bleeding wounds, iii) predominant zoophily,
and the association of high population densities during respective disease outbreaks, at least a veterinary meaning must be derived for viruses (equine infectious anemia virus, EIA virus), for bacteria (Bacillus anthracis, Francisella tularensis) as well as for certain protozoa of the genus Trypanosoma. Regarding anthrax only once from India species-related data were given for an outbreak, whereby Tabanus indianus, T. bicinctus (=T. biannularis) and Haematopota montana were incriminated. Eventually, in South America tabanids can act as phoretic vehicles for the eggs
of the myiasis-causing human bot-fly Dermatobia hominis.

Dusan Petric

Establishing of the dispersion capacity of Simulium ornatum Meigen, 1818 (complex) larve by application of methylen blue vital dye

Nina Pualić, Aleksandra Ignjatović Ćupina, Marija Zgomba, Dušan Petrić
University of Novi Sad, Faculty of Agriculture, Laboratory for Medical and Veterinary Entomology,T.D.Obradovića 8, 21000
Novi Sad, Serbia

Identification of the dispersion capacity of S. ornatum late instar larvae, by artificial positioning in the upstream uninhabited sections of the stream, distant from typical breeding zones was the main
objective of this study. Further more, the convenience of methylen blue vital marker application as a suitable tool in biological studies of black flies in natural environmental conditions was tested.
Larval marking was performed in methylen blue aqueous solution 25 mg/l and 45 minutes exposition. High portion of visually detectible dyed larvae (about 90%) was recorded, no mortality and high persistence of the dye in the larval body all over the 15 days period.
Tendency of dispersion and successive inhabitation of downstream sections at increasing distances was expressed in majority of larvae (99,33%). The increase of distances covered in function of time
was recorded, starting from 17 m to 93 m after 1 and 15 days, respectively.

Patricia Valle Trujillo

Colonisation patterns of Catalonia (northeast Spain) by the tiger mosquito (Aedes albopictus): trends from 2004 to 2008

Antoni Torrell, Jordi Ruiz, Mariano Rojo: Flora, Fauna and Pet Protection Service, Government of Catalonia, Barcelona, Spain.
Roger Eritja: Mosquito Control Service, Regional Council of El Baix Llobregat, Spain.
Eduard Marquès: Mosquito Control Service of Roses Bay and the Lower Ter, Castelló d’Empúries, Spain.
Presented by: Patricia Valle Trujillo: Public Health Manager – Kenogard Spain.

Aedes albopictus was initially detected in Spain in 2004 (Aranda et al.) in the municipality of St. Cugat del Vallès (Barcelona province). In the last 5 years, the tiger mosquito population has spread, and stable populations of this mosquito being currently to be found in 85 municipalities in Catalonia, potentially affecting over 4 million people.
2005 saw the establishment of a Working Group that comprises the Departments of Health and of the Environment of the Government of Catalonia, Barcelona Provincial Council, the Barcelona Public Health Agency, the Regional Councils of El Baix Llobregat (including the group Mosquito Control Service) and El Vallès Occidental and different municipalities where presence was potential.
To fight the tiger mosquito, this Working Party established the following priorities:

  • Communication of the problem, since some preventive control measures on a private level stem from notification.
  • Coordination of control work on a municipal scale.
  • Monitoring to determine dispersion and the colonisation of new sites by Aedes albopictus.
  • Advising population.

In 2005, ovitraps were used to characterise the tiger mosquito population in Catalonia and to accurately determine the municipalities affected and with what intensity.
The 2006 study left no doubt that the tiger mosquito was clearly expanding throughout Catalonia. Not only was it spreading like an oil stain; it was also travelling large distances, which was demonstrated by its presence in municipalities located several kilometres from the initial concentration.
In 2007, monitoring of the species continued to determine its evolution and its rate of expansion, bearing in mind the likelihood that the mosquito would continue to colonise new territories close to those already affected. Nonetheless, the possible appearance of concentrations that were isolated and distant from the risk
area also had to be considered.
The 2008 study has shown that the colonisation of new territories by this mosquito has not stopped, mainly because of: climate, the large number of available breeding sites, and the great mobility of vehicles in Catalonia.
A predictive model is being developed to asses the final scenario for the presence of the species.