Search

Background: Vector control of Malaria is mainly made by using impregnated bed nets and insecticides pulverizations indoor or/and outdoor. Besides, appearance and development of resistance’s phenomenon among mosquito populations to insecticides, constitute a significant obstacle this fighting. Aims: To highlighting a neutralization phenomenon of three insecticides (methyl-parathion, dimethoate and cypermethrin) during development of the Anopheles gambiae s.s. larvae. Methodology: Two setups followed one after the other were designed. In setup 1, four concentrations (with four replicates each) were freshly prepared and independently received a first batch of 100 first instars An. gambiae s.s. After emergence of adults from this first batch, the same test media were simply filtered and received a second batch of first instars larvae to make setup 2. Three endpoints were measured in this study: the duration of larval phase, the larval mortality, and the size of adults. Results: The development duration and mortality of larvae decreased significantly at setup 2 with cypermethrin and methyl-parathion. Thus, the duration of larval stage decreased from 10.18 days at setup 1 to 7.84 days at setup 2 for 0.010 µg/l (highest concentration) with cypermethrin and from 10.20 days at setup 1 to 8.27 days at setup 2 for 0.144 µg/l (highest concentration) with methyl-parathion. The larval mortality dropped from 79.32 % at setup 1 to 12.00 % at setup 2 for the highest concentration of cypermethrin and from 76.42 % at setup 1 to 12.50 % at setup 2 for the highest concentration of methyl-parathion. While adults size significantly increased in setup 2. For males, wing’s length increased from 3.28 mm at setup 1 to 3.49 mm at setup 2 for the highest concentration of cypermethrin, from 3.31 mm at setup 1 to 3.49 mm at setup 2 for the highest concentration of methyl-parathion. In female, wing’s length increased from 3.52 mm at setup 1 to 3.68 mm at setup 2 for the highest concentration of cypermethrin, from 3.49 mm at setup 1 to 3.68 mm at setup 2 for the highest concentration of methyl-parathion. Conclusion: This work shows that mosquito larvae, especially An. gambiae are able to modify breeding medium to improve its fitness during their development.

Background: The present work aimed to highlight process of transmission of tolerance to insecticides in An. gambiae population over several generations. Methodology: The experiment was carried out at the laboratory with the strain of An. gambiae that was continuously raised under laboratory conditions for more than five years. The insecticides used during this study belong to three families: methyl-parathion (carbamates), dimethoate (organophosphate), and cypermethrin (pyrethroids). For each insecticide we chose the concentration of insecticide able to exert a selective pressure on An. gambiae without inducing a total mortality. The experiment was done through 12 consecutive generations of An. gambiae s.s. the Endpoints measured: the duration of larval development, larval mortality, and the size of adults. Results: For cypermethrin (pyrethroid) and methyl-parathion (carbamates), the development duration of the larval phase as well as larval mortality decreases significantly from the 7th generation onwards. In the other hand, the size of the adults increases significantly as early as the 5th generation for females especially for cypermethrin and the 7th generation for males. However, with dimethoate, the duration of the larval phase did not vary significantly over the generations. A decrease in larval mortality was noted from the 8th generation but it remained too high. Adult size also increased significantly from the 8th generation onward in both the two genera. This work showed the improvement over generations of certain biological indicators of the resistance. Thus, Conclusion: we can state that resistance appears fairly early in An. gambiae s.s., especially for insecticides that are effective at low doses, such as cypermethrin and methyl-parathion

Aims: This study aimed to investigate the levels of efficacy of anthelmintics that were most commonly used in sheep farms in Nziih locality. Study Design: Longitudinal prospective study. Place and Duration of Study: The study was carried out in Nziih locality in August 2019 and September 2020. Methodology: Resistance against Albendazole (12.5 mg/kg) and Ivermectin (0.2 mg/kg) was evaluated using faecal egg count reduction test in naturally occurring gastrointestinal strongyles of sheep in Nziih. A total of 300 young animals were randomly selected from 5 farms in 2019 and in 2020. Faecal samples were collected from each animal on the first day of treatment (D0) and collected again 14 days later (D14). Faecal Egg Counts were performed using the Willis and Mac Master techniques and resistance was declared when faecal egg count reduction (FECR) was less than 95 % and the lower limit of confidence interval (LCI) less than 90%. Pooled faecal samples for each treatment group were set for D0 and D14 to identify resistant strongyles genera by calculating persistent larval rate (PLR). Results: Resistance against Ivermectin was detected while there was none against Albendazole. Moreover, it was declared only in 2 farms out of the 5 selected. From 2019 to 2020, the status of resistance has shifted from suspicion to resistance for ivermectin and from absence of resistance to suspicion to Albendazole. Resistance was recorded in 2 sites: Pastorale1 (FECR= 85 %, LCI= 42.61 %) and Pastorale 3 (FECR=90.5 %, LCI= 72.26 %) in large flock herds and in farms where sheep were dewormed at least 4 times per year. Trichostrongylus were more persistent than Haemonchus and Oesophagostomum/Chabertia with PLR of 21.22 %, 13.71 %, and 7.40 % respectively. Conclusion: Anthelmintics must be used correctly in conjunction with farmer education in Nziih.

Background: Soil-transmitted helminths (STHs) continue to be a public health problem in developing countries. In Bandjoun, annual deworming is usually administered to school-age children through the national programme for the control of schistosomiasis and soil-transmitted helminthiasis in Cameroon. However, official data on the level of STH infections are scarce in this locality. Methods: We investigated the prevalence and associated risk factors of STHs among children in Bandjoun with the intention to help design future intervention plans. We obtained demographic data and potential risk factors through the interview of children using a structured questionnaire. Stool samples from these children were collected and examined for helminth eggs using Willis’ technique. Results: Three STHs were identified with an overall prevalence of 8.7%. These nematodes were Ascaris lumbricoides (8.3%), Trichuris trichiura (0.3%) and hookworms (Ancylostoma duodenale, Necator americanus) (0.7%). Failure to wash hands before meals (AOR: 2.152 [1.056-4.389]) was the main predictor associated with Ascaris infections. Not eating food picked up from the ground (AOR: 0.494 [0.261-0.937]) and not raising pigs at home (AOR: 0.109 [0.045-0.268]) reduced risk of infection. Conclusion: We recommend that STHs control interventions in Bandjoun focus on the good management of domesticated pigs, the avoidance of contact with soil and handwashing from the earliest ages as a part of daily hygiene practice.

Background: Soil transmitted helminth infections are Neglected Tropical Diseases (NTD) affecting mostly pupils in developing countries. They seem to lose more and more interest due to the fact that resources and research are being justifiably diverted to more recent priorities such as HIV/AIDS, cancers, tuberculosis and malaria. As a result, specific data on STH infections is often lacking. Aims: To evaluate the prevalence and intensities of STH parasites among pupils in Penka-Michel Sub-division, West-Cameroon in order to refresh information for a better management of these parasitic diseases. Settings and Design: A cross-sectional analytic study was conducted from October to December 2018 in Penka-Michel Sub-division. Methods and Materials: To evaluate the prevalence and intensities of STH parasites among pupils, seven hundred and twenty nine (729) stool samples were collected from pupils aged 4 to 14 years old in 23 randomly selected primary schools. The samples were analysed using the concentration method of Willis and the Mc Master technic. Results: Out of 729 pupils enrolled, 107 (14.7%) were infected with one or more STH parasite species. The nematodes species identified were Ascaris lumbricoides (9.9%), Trichuris trichiura (5.3%) and hookworms (2.2%). Pupils aged from 8 to 11 years were the most infected (17.3%). Statistically females were more infected with hookworms (2.2%). These parasites occurred as monospecific (84.11%), bi-specific (13.0%) and tri-specific (2.80%) infections. The mean fecal eggs count was 3652.78±8715.93, 266.67±273.81 and 118.75±72.74 for A. lumbricoides, T. trichiura and hookworm respectively. According to faecal concentration of eggs, 88.18% of infections were light. Conclusion: These results show the necessity of sustainable application of regular deworming, health education and improvements in sanitation among pupils in Penka-Michel Sub-division.

Introduction: Gastrointestinal nematodes have a deleterious effect on animal health and production. In search of alternative to synthetic anthelminthics in the control of strongylosis among small ruminants, this study was conducted to evaluate the in situ adulticidal properties of Moringa oleifera on gastro-intestinal strongyles of goats. Methods: Twenty (20) goats naturally infested with mixed gastrointestinal nematodes were distributed into 5 groups (n=4): a negative control group receiving Tween 80 at 2.8%, a positive control group treated with Albendazole at 5 mg/kg and tested groups treated with doses of extract (125, 250 and 500 mg/kg). In situ anthelminthic activity was assessed through determination of the faecal eggs count reduction, total worm count reduction, variation of packed cell volume (PCV) and body weight after treatment. Results: Five species of nematodes were identified among experimental animals, with Strongyloides papillorus as the most prevalent (93.8%) followed by Haemonchus contortus (87.5%). At dose of 500 mg/kg, ethanolic extract of M. oleifera registered 76.4 % and 69.8 % eggs density reduction of gastro-intestinal strongyles eggs and parasitic load nineteen days post-treatment respectively while Albendazole induced 100 % reduction of these same parameters at the dose of 5 mg/kg. Moreover, the extract did not significantly affect PCV nor body weight of experimental goats. Conclusion: This study validates scientifically the use of alcoholic leaves extract of M. oleifera in the treatment of gastro-intestinal strongyles. The standardization of this extract is however necessary for his use as a sustainable tool for controlling strongylosis in small ruminants.

Background In Cameroon, considerable research has been conducted on human ascariasis, but no studies have been undertaken to determine whether pigs contribute to the persistence of the infection in children or to unravel the evolutionary relationship between human-derived and pig-derived Ascaris. Methods DNA was extracted from adult Ascaris worms collected from humans and pigs. Segments of the cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes were sequenced and analysed for 83 worms to dissect the local transmission dynamics of Ascaris in Cameroon. Results The data showed high genetic diversity and revealed demographically expanding populations in the human and pig Ascaris samples. A restricted gene flow between Ascaris lumbricoides and Ascaris suum populations correlating with the preference for humans and pigs, respectively, as hosts was evident. Phylogenetic analyses and haplotype networks split the haplotypes into two major clusters, A and B. However, support for cross-transmission between hosts and hybridization were revealed through shared haplotypes among worms from both hosts. Conclusions This study provides useful baseline information for future studies of the genetics of Ascaris in Cameroon and suggests that effective and sustainable control of human ascariasis should target both human and pig hosts.

Previous studies have reported interactions between Salmonella spp. and some helminth coinfections. In this study, S. typhimurium and Ascaridia galli coinfections were analyzed, and the consequences on therapy were proposed. In a first experiment where the effect of the bacteria on the nematode was evaluated, thirty 42-day-old broiler chickens were divided into 3 groups and coinfected with both parasites. The rate of A. galli egg inoculum was kept constant at 500/ml while that of S. typhimurium varied as follows: T0 (500 A. galli eggs/ml), T104 (500 A. galli eggs/ml+104 S. typhimurium CFUs), and T106 (500 A. galli eggs/ml +106S. typhymurium CFUs). EPG and parasitic load were measured using the McMaster technic, and number of worms and their length were also measured. We observed that T106 containing 106 CFUs of Salmonella significantly reduced the EPG values, and this group recorded the lowest worm load ranging from 18 to 21 worms. Likewise, the length of the worms obtained with T104 and T106 appeared to be shorter than those of the control (T0). In a second experiment to assess the effects of the nematode on the bacteria, thirty 42-day-old broiler chickens were divided into 3 groups and coinfected with both parasites. The rate of S. typhimurium inoculum was kept constant at 106 CFUs while that of A. galli varied as follows: T0 (106CFUs), T500 (500 A. galli eggs/ml +106S. typhymurium CFUs), and T750 (750 A. galli eggs/ml +106S. typhymurium CFUs). Bacterial load was measured using Voogt technique. We observed that T500 increased the colonization time and prolonged the duration of S. typhimurium secretion. Salmonella appears to be a hyperparasite considering the deleterious effect on A. galli. Due to this, it may be prudent to combine anti-Salmonella treatment with anthelmintic so as to effectively treat pathologies caused by these two pathogens.

Previous studies have reported interactions between Salmonella spp. and some helminth coinfections. In this study, S. typhimurium and Ascaridia galli coinfections were analyzed, and the consequences on therapy were proposed. In a first experiment where the effect of the bacteria on the nematode was evaluated, thirty 42-day-old broiler chickens were divided into 3 groups and coinfected with both parasites. The rate of A. galli egg inoculum was kept constant at 500/ml while that of S. typhimurium varied as follows: T0 (500 A. galli eggs/ml), T104 (500 A. galli eggs/ml+104 S. typhimurium CFUs), and T106 (500 A. galli eggs/ml +106S. typhymurium CFUs). EPG and parasitic load were measured using the McMaster technic, and number of worms and their length were also measured. We observed that T106 containing 106 CFUs of Salmonella significantly reduced the EPG values, and this group recorded the lowest worm load ranging from 18 to 21 worms. Likewise, the length of the worms obtained with T104 and T106 appeared to be shorter than those of the control (T0). In a second experiment to assess the effects of the nematode on the bacteria, thirty 42-day-old broiler chickens were divided into 3 groups and coinfected with both parasites. The rate of S. typhimurium inoculum was kept constant at 106 CFUs while that of A. galli varied as follows: T0 (106CFUs), T500 (500 A. galli eggs/ml +106S. typhymurium CFUs), and T750 (750 A. galli eggs/ml +106S. typhymurium CFUs). Bacterial load was measured using Voogt technique. We observed that T500 increased the colonization time and prolonged the duration of S. typhimurium secretion. Salmonella appears to be a hyperparasite considering the deleterious effect on A. galli. Due to this, it may be prudent to combine anti-Salmonella treatment with anthelmintic so as to effectively treat pathologies caused by these two pathogens.

Background. One of the most dangerous Plasmodium species is Plasmodium falciparum. Hence, it causes a higher rate of mortality. The resistance of Plasmodium falciparum to the ACT (Artemisinin-based Combination Therapies) has led to the search for new antimalarial drugs. The purpose of this research was to assess the in vivo antiplasmodial activity of Entandrophragma cylindricum ethyl acetate extract to provide a scientific basis for the use of this medicinal plant to treat malaria. Methods. Entandrophragma cylindricum stem bark powder was macerated in ethyl acetate to obtain the extract. The extract liquid filtrate was concentrated, evaporated and dry using a Rotavapor. The Peter and Rane test were used for the suppressive and curative antiplasmodial activities at different doses (125, 250 and 500 mg/kg). A positive and negative control groups were administered chloroquine (5 mg/kg) and 10% hypromelose, respectively. To assess the parasitemia of the mice a thin blood smear was made. Results. The ethyl acetate extract completely (100%) inhibited the development of P. berghei in the suppressive test at the dose of 500 mg/kg while that of the curative test was inhibited at 95%. The extract-treated group (500 mg/kg) and (Chloroquine (5 mg/kg) group all survived. The negative control group recorded a 100% mortality rate. Conclusion. The present study provides scientific confirmation on the use of E. cylindricum stem bark as an antiplasmodial remedy. However, the identification of the mode of action and the purification of the active compounds are necessary for further studies.

Worldwide understorey nesting bird species such as bulbuls can also be highly vulnerable to nest predation in disturbed landscapes because they breed mainly on the lower stage of the forest. We test the following hypotheses: the transformation of forests into alternative land use systems and the vegetation’s variables at the nesting sites will affect the understorey nest predation rates. The nests of 12 understorey bird species were surveyed and vegetation variables were measured within five types of habitats along a gradient of increasing forest destruction in the north-eastern peripheral zone of the Korup National Park in Cameroon. Only the open-cup nest type suffers from predation, mostly egg predation. The general linear mixed model analysis suggests that the types of habitat do not affect nest daily predation rate which decreases with increasing trees and understorey plant density. The most deleterious impact of deforestation in this study area is the reduction of nesting sites whose characteristics remain unchanged across the landscape. These results underscore the need to give understorey nesting species, as well as other particularly sensitive groups, special consideration within conservation strategies such as the reduced-impact logging techniques. Key words: Cameroon, deforestation, land-use system, nest predation, understorey birds.

This study was carried out in Korup Region to investigate the reasons for hunting preuss’s red colobus (PRC) in Korup National Park (KNP) Cameroon in order to contribute to its sustainable management. Questionnaires (open and closed end) were used to gather personal information from hunters on different hunting tactics, reasons for hunting PRC and threats to this species in KNP for a period of one month (January 2014). One hundred and eighty-seven hunters responded to questionnaires that were distributed in all 5 villages in the park and 5 other villages randomly selected from the 23 villages surrounding KNP. Excel software was used and all variables were used to calculate relative proportions. Results showed that 53.5% of hunters use shotguns and 46.5% use both shotgun and wire snares in hunting. Majority of the hunters (46%) practice both hunting and farming, 32% practice solely hunting, 18% practice hunting and fishing, and 4% practice hunting, farming and fishing. A large proportion (73.3%) of hunters does hunt PRC for protein and income. However, 45.3% of them do not eat PRC because of its bad odour, and 22% do not eat it because the meat is hard. Hunters in KNP depend on hunting for their survival. Therefore, this calls for conservation action, such as introducing an alternative source of livelihood and protein to hunters, which will help to improve their standard of living and supply protein for their healthy growth, thereby discouraging hunting. Key words: Hunting, Korup National Park, anthropogenic activity, survival, Procolobus preussi.

Background The resistance of some medico-veterinary parasite strains as well as the unavailability and toxicity of synthetic anthelminthics on humans, animals and the impacts of their residues in the environment have pushed scientists to turn to plants with anthelminthic properties. Hence, the aim of this work was to contribute to the fight against helminths of medical and veterinary importance in general, and also to clear the environment of their free living stages. Methods Fresh eggs of Heligmosomoides bakeri were obtained from the faeces of experimentally infected mice. L1 and L2 larval stages were obtained after 48 and 72 h of coproculture respectively. Methylene Chloride-Methanol (1:1) extracts of Annona senegalensis and Nauclea latifolia were diluted in DMSO or Tween 80 to prepare the following concentrations: 625, 1250, 2500, 3750 and 5000 μg/ml. The effects of extract solutions were evaluated on the embryonation of eggs, egg hatching and on L1 and L2 survival after 48, 10 and 24 h of incubation. Negative controls were 1.5% DMSO, 4% Tween 80 and a mixture of these solvents. The TLC was carried out and the profiles of secondary metabolites were made. Results Negative controls had no effect on the embryonation, eggs hatching and on larval mortality. However, it was found that, the extracts affected the free living stages of H. bakeri in a concentration-dependant manner. At the highest concentration (5000 μg/ml), the rate of inhibition of embryonation obtained were 20.80%, 38.15% and 84.83% for Methylene Chloride-Methanol of Annona senegalensis (MCM As), Nauclea latifolia (MCM Nl) extracts and mixture of Annona senegalensis and Nauclea latifolia (MCM As-Nl) extract respectively. For egg hatch, the inhibition rate was 16.10%, 46.24% and 87.07% for the above three extracts respectively at the same concentration of 5000 μg/ml. On L1 and L2 larval stages after 24 h of exposure to extracts, the mortality rates of 100%, 54.76% and 96.77% against 98%, 51.44% and 100% were obtained for MCM As, MCM Nl and MCM As-Nl respectively at the highest concentration. The Methylene Chloride-Methanol of A.senegalensis, N. latifolia extracts showed the presence of alkaloids except in N. latifolia extract, flavonoids, sterols, triterpens, tanins, polyphenols, anthraquinons, saponins and terpenoids. Conclusion These findings suggest that, the mixture of the two plant extracts showed an additive (synergetic effect) ovicidal effect and a slight larval mortality on L1 as compared to the effect of MCM As extract alone. These effects were due to the presence ao secondary metabolites identifies in the plant extracts. Thus, they may be used as possible «disinfectants» for soil transmitted nematodes.

Background. Malaria is one of the most critical diseases causing about 219 million cases worldwide in developing countries. The spread and development of resistance against chemical antimalarial drugs is one of the major problems associated with malaria control. The present study was to investigate the antimalarial efficacy of ethyl acetate extract and one fraction of Bidens pilosa in vivo in order to support the usage of this plant by traditional healers to treat malaria. Methods. The extracts were prepared by maceration of B. pilosa leaf powder in ethyl acetate. The liquid filtrate of the extract and the best in vitro antiplasmodial fraction using HPLC were concentrated and evaporated using a rotavapor under vacuum to dryness. The antimalarial activity of B. pilosa plant products were evaluated in vivo against Plasmodium berghei infected mice according to the Peter and Rane test. The antimalarial efficacy of the a selected crude extract (ethyl acetate extract) was evaluated at 125, 250, and 500 mg/kg, while a selected fraction from ethyl acetate extract (fraction 12) was evaluated at 62.5 and 125 mg/kg. Blood from experimental animals was collected to assess hematological parameters. Results. The crude extract of ethyl acetate and fraction 12 demonstrated 100% in vivo parasite suppressive activity at doses of 500 mg/kg and 125 mg/kg, respectively, for the crude extract and fraction 12. The mice treated with 250 and 500 mg/kg had their parasitemia (intraerythrocytic phase of P. Berghei) drop considerably, disappearing by the 8th day in mice receiving 500 mg/kg. The ethyl acetate extract of B. pilosa, fraction 12 showed an even higher antiplasmodial activity. By the 5th day of the experiment, the treatment led to a modification of hematological parameters in mice. The chloroquine (5 mg/kg), fraction 12 (125 mg/kg), and the crude extract (500 mg/kg) groups all survived the 30 days of the experiment, while the negative control group registered 100% of the deaths. Conclusion. This study scientifically supports the use of Bidens pilosa leaves in the traditional treatment of malaria. However, the mode of action and in vivo toxicity of the plant still need to be assessed.

Additional file 3: Table S3. Concordance between RDT and PCR targeting T. b. gambiense.

Additional file 2: Table S2. Concordance between RDT and PCR targeting all trypanosome species.

Additional file 1: Table S1. Concordance between CTC and RDT.

Eyprepocnemis plorans ibandana is a very common grasshopper species in open environments and agricultural systems of tropical Africa. It is a pest that significantly benefits from forest degradation in southern Cameroon, hence the need to study the bioecology of this subspecies. We studied the reproduction as well as the morphological characteristics and development times of the post-embryonic instars of E. p. ibandana. Sixty-one adult pairs were obtained from sixth instar nymphs caught in grassy vegetation in the Nkolbisson area (Yaoundé) and bred in the laboratory. After hatching, the first instar nymphs were individually placed in cages and fed every two days using fresh leaves of Manihot esculenta. The postembryonic development of E. p. ibandana took six instars in the male and six to seven instars in the female. Mean nymphal development took 79.16 ± 0.51 days in males, 89.93 ± 0.58 days in 6 instar females and 94.96 ± 1.22 days in 7 instar females. The survival rate of the first instar was low (53%). However, from the second instar on the survival rate was very high (> 87%). Sexual dimorphism is distinct in adults, fifth and sixth nymphal instars. Adults of E. p. ibandana took on average 32.57 ± 3.88 days to start mating, and mating lasted 2.12 h on average (1–3 h). Oviposition took place on average 52.03 ± 5 days after first mating; each female deposited one to eleven oothecae with an average of 34.93 ± 2.37 eggs per ootheca. Our study provides important information for the control of this subspecies in southern Cameroon.

Background: Soil transmitted helminth (STH) infections disproportionately affect poor populations in tropical and subtropical parts of the world. They contaminate soil and pupils are mostly at risk of these infections due to their soil related habits. Aims: to assess pupils’ knowledge, attitude and practice in relation to the rate of soil contamination in public primary schools. Methods: Structured questionnaires were administered to 729 consenting participants to obtain information on their awareness status of STH infections. A total of 552 soil samples were collected around toilets, classrooms backyards and playground in 23 public schools randomly selected in Penka-Michel subdivision and examined for the presence of STH eggs using the sucrose flotation method. Results: up to 80% of respondents do not actually know how to avoid getting infected with worms. About 50% of pupils do not actually wash their hands after defecating or wash their fruits/vegetables before eating. Pupil’s nails were mostly untrimmed (74.1%). 77.1% declared they always defecate out of the toilets when they are in school. Out of 552 soil samples examined, 97 (17.6%) were contaminated by Ascaris sp, Trichuris sp, Toxocara sp, Capillaria sp, Cooperia sp, hokworms and Nematodirus sp. Soil from around toilets were significantly more contaminated with Ascaris sp and Trichuris sp eggs. Soil contamination was also significantly associated with absence of water during class hours, unhygienic conditions of toilets, and lack of school perimeter fence. Overall 65% of schools selected showed a low level of hygiene. Conclusion: Pupils of these schools played a major role in the contamination of their environment. Therefore, in order to prevent the STHs transmission cycles in school environment and possibly in pupils, it is necessary to develop specific sustainable intervention programs.