211 research outputs found
Controlling disease in migratory bird population- a probable solution through mathematical study
No full textThe role of migratory birds in an eco-system cannot be ignored. It becomes more important if they carry a disease. Chatterjee and Chattopadhyay proposed and analysed a three component one season eco-epidemiological model consisting of susceptible migratory birds, infective migratory birds and their predator population (see Chatterjee, S. and Chattopadhyay, J., Role of migratory bird populations in a simple eco-epidemiological model, Mathematical and Computer Modelling of Dynamical systems, in press). They assumed that the recovered infective birds become susceptible again. But, it is observed that in diseases like salmonella and WNV, the recovered birds develop a permanent immunity. Keeping this in mind we modify the model of Chatterjee and Chattopadhyay by adding a recovered class. The main objective of this work is to observe the role of recovery and immunity in such a system. Numerical simulations for a hypothetical set of parameter values are presented to illustrate the analytical findings. It is observed that to obtain a disease free system proper vaccination and proper predation are necessary. The second factor was mentioned in the paper of Chatterjee and Chattopadhyay
Primary prevention of ocular injury in agricultural workers with safety eyewear
No full textPurpose: The purpose of this study was to determine the effectiveness of preventing eye injury with the use of safety eyewear in agriculture workers. Methods: A sample group of 575 agricultural workers (Group A) engaged in harvesting paddy were provided with goggles with side covers. Following harvesting, a questionnaire-based survey was carried out to determine the frequency of their eye injuries. Workers with goggles were asked about the duration for which they used the goggles and also list barriers or difficulties with the same. The frequency of eye injuries in this group was compared with another group of agriculture workers (Group B) who did not use any safety eyewear. Results: The frequency of eye injuries in Group A was 4 (0.7%) and Group B was 61 (11.3%) which was highly significant (P = 0.0001). The relative risk calculated was 0.06 (95% confidence interval: 0.02–0.2). Agricultural workers in Group A had 94% less risk of ocular trauma compared to those in Group B. Injuries in both groups were caused by parts of the paddy plant. A significant number (76.2%) of workers used the goggles all or most of the time during work. Impaired vision when wearing goggles was the most frequent barrier reported by the workers. Other barriers were discomfort, shyness, forgetfulness, apathy, slowing of work pace, awkward appearance, and breakages. Conclusion: Safety eyewear conferred significant protection against work-related eye injuries in agriculture. Although safety eyewear was widely adopted by the workers, barriers reported by them will need to be addressed to make such programs more effective
Multi-drug resistant Pseudomonas aeruginosa keratitis and its effective treatment with topical colistimethate
No full textThe purpose was to evaluate the clinical outcome in multi-drug resistant Pseudomonas aeruginosa (MDR-PA) bacterial keratitis and report the successful use of an alternative antibiotic, topical colistimethate in some of them. The medical records of 12 culture-proven MDR-PA keratitis patients, all exhibiting in vitro resistance by Kirby–Bauer disc diffusion method to ≥ three classes of routinely used topical antibiotics were reviewed. Eight patients were treated with 0.3% ciprofloxacin or ofloxacin, 1 patient with 5% imipenem/cilastatin and 3 patients with 1.6% colistimethate. The outcomes in 8 eyes treated with only fluoroquinolones were evisceration in 4 eyes, therapeutic corneal graft in 1 eye, phthisis bulbi in 1 eye, and no improvement in 2 eyes. The eye treated with imipenem/cilastin required a therapeutic corneal graft. All the three eyes treated with 1.6% colistimethate healed. Colistimethate may prove to be an effective alternative antibiotic in the treatment of MDR-PA keratitis
Characteristics of Human-Tiger Conflicts in Indian Sundarban
No full textThe Sundarban, spread across India and Bangladesh constitutes the world’s largest and only mangrove habitat of the Royal Bengal Tiger (Panthera tigris tigris). Together, harbouring around 202 tigers, it is also infamous as the worlds most severe human-tiger conflict hotspot. Despite this, very fragmentary and inconsistent information exists on the nature and extent of human-tiger conflicts (HTC) in this landscape. To fill this lacuna, a pan landscape survey was undertaken with the aim to mine information on HTC and explore various facets of HTC occurrence in this landscape. The survey was conducted across 76 villages distributed in the eight administrative blocks on the entire fringe of the Sundarban Biosphere Reserve in India between August 2018 to November 2019.
On the whole, human-tiger conflicts (HTC) were reported far more commonly than cases pertaining to conflicts with crocodiles and sharks (species unidentified). The number of cases of human-wildlife conflicts (HWC) recorded were highest in the Gosaba administrative block, followed by Kultali and Patharpratima, which together account for 74% of the recorded cases. This is interesting as in earlier published records almost no consolidated information exists for the south-24-Parganas Forest Division, although it appears that the two administrative blocks here experience the second highest level of HTC in this landscape after Goasba, in north 24 Parganas.
Across the forty-year period span of the recorded information, the overall conflicts between humans and tigers appeared to have witnessed a significant increase after 1987. However, this is most likely a result of poor documentation and relatively low probability of people recalling older incidents accurately. The time series change also shows a significant lowering of human-tiger conflicts post year 2000 (Ref. Figure 1.3), which is suggestive of changes brought about by stronger enforcement as well as the beginning of the arrangements for barricading the fringes with nylon nets (Tiger Conservation Plan, STR, 2012; also see, Mukherjee et al., 2012). The level of conflict between humans and crocodiles and humans and sharks, however, did not show significant changes across the same period. The significant lowering of HTC cases held statistically, even when the data was compared across decadal periods. Post completion of the survey, between 1st December 2019 and 31st October 2020, another 22 cases have been recorded, 21 of which resulted in the death of the victims involved. However, these could not be included in the analysis due to the absence of detailed information, which could not be collected due to the paucity of time (and subsequent Covid-19 driven restrictions).
Most victims of HTC were males (92%), across all age categories of victims, and the majority of the victims belonged to the working age-class, i.e. 19 to 60 years. On average, HTC victims had at least 5 dependent family members, with majority below the poverty line (BPL, as per classification of Govt. of India), earning on average Rs. 25000 (~ USD 336) per annum. Majority of the victims belonged to classified Schedule Caste groups (~69%) and Other Backward Classes (~13%), while only about ~8% belonged to classified Scheduled Tribal groups (indigenous people). This, however, could simply be reflective of the proportional distribution of the various categories in the region. However, a deeper analysis suggests that across the villages surveyed, those with a higher population of Scheduled Tribes experienced a lowered level of HTC, probably indicating that Scheduled Tribes’ are not engaged extensively in natural resource collection compared to other ethnic populations.
90.14% of the victims were Hindus, and only 9.9% of the victims were Muslim and Christian. Compared to the distribution of different religious groups, where Muslims constitute around 30% of the population of south 24 Parganas, their representation in the sample of victims was relatively low at 9.5% of the total number of victims recorded. Irrespective of the religious background of victims, the majority of HTC victims were illiterate (64 – 77.8%), and around 79% of the victims were dependent on forest-based livelihoods, primarily fishing, crab and prawn collection and honey collection as the primary source of their income.
Although around 52.4% of the victims/victim’s family, reported to be owning tillable agriculture land, the average land holding was 0.2 acres, which is extremely small to provide sustainable income from traditional agricultural practices. Further, during interviews, several people reported an increased salinity in their lands due to the inundation of bunds/dykes during natural calamities, leading to saline water inflow into their lands. Such increased salinity of land often renders the land unfit for agriculture. Only 15.6% of the victims or their families owned a fishing boat, indicating that even the majority who were forest-based resource dependent, relied on borrowing or renting boats locally.
An independent analysis using the survey data and the populations statistics data from the Census of India, 2011, suggested some interesting trends. Illiteracy, and marginal occupations such as agricultural wage labour, impacted the level of conflicts that people of surveyed villages experienced. It is intuitive that such populations will be forced to depend extensively on natural resource collections to supplement their livelihoods, and thus become an economic section that is specifically vulnerable to HTC.
Further, it is not surprising that most of the victims were dependent on forest-based livelihoods, and majority of the HTC cases (~91%) were reported to have occurred either in the core area, or in the buffer areas (reserve forests). About 62% of the cases that recorded to have occurred in village lands (n = 42), were from 1980 to 2000, while the remaining were reported between 2001 and 2012, with only 10 cases (23.8%) after 2001. It must be noted that by 2012, the nylon net barrier establishment was complete across an exceptionally large section of the fringe forests, effectively preventing tigers from moving out of forests and into villages. However, a few tigers occasionally still manage to come out of the forests each year, even to this day. Since 2010, the West Bengal Forest Department has also been effectively managing to either drive tigers back, or in capturing them from villages and releasing them back into the forests. Nevertheless, the data is supportive of the fact that in Sundarban, unlike some other Tiger Reserves of India, majority of the cases occur when people enter forests for various purposes. It was also observed that the majority of the cases that were reported to have occurred inside the forests (core or buffer) or even in open waters, most resulted in the death of the victims, when compared to the incidents reported to have occurred in the village areas (See figure 1.5). This is understandable, as in village areas help is closer at hand, than compared to when victims encounter tigers away from human habitations. This was further corroborated by the observation that during the HTC incidents occurring in the villages, the average number of people present near the victim was around ~16 people. Comparatively, the average number of people present with the victim in incidents that occurred away from village areas was 4.9 ± 2.7 people.
The average group size of people also appeared to be correlated to the occupation that victims were pursuing. Besides, farming, which due to its locational specificity ensures a larger mass of people around any potential victim at any given point of time, different predominant forest-based livelihoods pursuits entailed varying sizes of aggregation of people (see figure 1.10). By far, honey collection seemed to accrue larger aggregations, as the number of eyewitnesses present around HTC victims who had reportedly gone into forests to collect honey were significantly higher than number of people present with victims who went into forests to fish, collect prawns or crabs. People venturing into forests to collect crabs also had relatively smaller aggregations compared to the victims who went to forests to collect prawns, honey or for fishing. This is understandable as most forest-based livelihoods are undertaken in groups, rather than by people individually. This is especially true for honey collection, as the period of honey collection is confined to 3-4 months a year, witnessing a larger number of collectors entering the forest, often camping for several days and nights, and hauling large caches of honey collected from natural Apis Dorsata hives. On the other hand, crab collection requires less people compared to all the other forest resources to increase catch sizes. Crab collection is typically carried out by groups of 3-4 people who venture into suitable areas in the forest, usually narrow creeks, positioning themselves over burrow openings inside natural pools to lift crabs out by attaching baits at the end of handheld fishing lines (Pers. Obs.). Crabs being extremely sensitive to vibrations, a minimal group size of people is required to optimise catch sizes in single hauls. Prawn fishing on the other hand is usually done sitting atop boats while shrimp fry are caught by wading through relatively shallow waters using a fine fish net. Fishing is also popularly carried out using cast nets and is carried with fewer people. Added to the increased vulnerability that smaller groups face, the commercial demand for certain resources such as tiger prawns, crabs, certain species of fish, forces people dependent on these resources for livelihoods, to put in more time trying to harvest them. Consequently, many resource collectors today often spend multiple days inside forests in attempts to collect large catches and thus bring lucrative returns, despite the entailing higher risks of tiger attacks.
Thus, most victims died due to HTC incidents when involved in the collection of forest-based resources, compared to when farming in the village lands (See figure 1.5), and most of the victims attacked when they were either on the ground or on boats. Rarely were they attacked when in the water (Figure 1.6). Interestingly, most victims were also attacked by tigers when they were walking or standing erect on the ground, or in the water. This is contrary to findings from other places, such as the Terai belt, where majority of victims were attacked by tigers when in a crouching position (Chatterjee et al. 2017). Victims who were attacked when on their boats were in a sitting or crouching position when attacked, but the overall proportion of such cases was relatively low (see Figure 1.9). It may be noted here that the ground substrate of most of the areas of Sundarban forests is comprised of such soft clay that human feet invariably sink deep into it, making travelling an arduous task, and intuitively making people standing in, or walking appear short. It is interesting to note, that when the influence of posture (standing, squatting, lying), substrate (ground, water, boat) and the group size present with the victim during the incident, on the outcome of the incident (death or survived), was investigated, both posture and group size had a significant impact on people dying as a result of an attack. This meant that irrespective of the substrate people were situated upon, their probability of dying as a result of the attack increased with changing posture (standing < squatting < lying) and decreasing number of people resent with the victim.
Another interesting finding is that over the four decadal periods, the number of victims of HTC who ventured when fishing appeared to have significantly decreased, compared to victims venturing for crab collection, which contrarily to this observation, appeared to have increased over time (Figure 1.14). This is likely to be indicative of the changing trends, wherein crab collection in recent times has become a lucrative source of income due to an increase in demand for different edible estuarine crab species (Choudhury et al. 2008).
Thus, several aspects appeared to be responsible for increasing the probability of being attacked, the most important of these appeared to be the presence of people in the forest, being on the ground in a standing position, and in smaller group sizes. Most people who died were in smaller group sizes, or in other words, the average group size of people present with the HTC victims who were rescued and survived to tell the tale of the incident where significantly larger, compared to the average group size present with people who died on the spot or were rescued and died enroute (Figure 1.10).
Further, interestingly, 60% of the rescued and surviving victims, also received timely medical aid and treatment, while only around 37.5% of the victims who were rescued but died, had received any form of medical attention (Figure 1.16). This suggests that the availability of medical facilities plays a crucial role in determining if a victim rescued from an HTC incident will survive or not, although the severity of the injuries is also likely to play a key role in the death or survival of the victim. Lastly, most HTC incidents were recorded roughly during the early morning hours to midday, with a significant drop in cases recorded to have occurred in the afternoon, evening, or night. This is because most people venture out into forests exceedingly early, often before dawn in this region, which could be a direct implication of the sweltering heat that this region experiences almost throughout the year, or as a strategy to avoid being detected by the patrol boats of the forest department. Nevertheless, this period of human activity in the forests, also closely coincides with the activity pattern of tigers here as suggested by Naha et al.’s study of radio-collared tigers in this landscape (Naha et al. 2016). Such overlap of activity periods may increase the chances of negative encounters between people and tigers.
While it is understood that various other ecological factors also may have an important role as ultimate drivers of HTC, it is clear from the current survey results that the socio-economic status of villagers living on the fringe, especially their low-income occupations are primary drivers of HTC in this landscape. While, posture, substrate, time of forest visit, etc., can all be key drivers of adverse outcomes of individual encounters, the sheer low number of HTC incidents that occur outside protected forest boundaries bears witness to the fact that Sundarban’s infamous image as a conflict hotspot, is primarily because people venture into the forests. Local communities’ dependence on natural resources to offset low incomes from marginal occupations such as wage labour, is the main reason for people falling prey to tiger attacks. Therefore, it is imperative that all conflict mitigation initiatives in this landscape must make a concerted approach to alleviate the lives of local people such that they can live sustainably and well, without depending on forest-based natural resources as a primary source of income
Fungal keratitis in Lattice dystrophy
No full textWe report a case of fungal keratitis occurring in a patient with lattice dystrophy. A 57-year-old farmer presented with a corneal ulcer following probable entry of paddy husk in the right eye, of one month duration. Corneal scraping revealed pigmented fungal filaments while culture grew Alternaria alternata. Treatment with 5% natamycin eye drops and 1% atropine healed the infection in four weeks. We would like to draw attention to the fact that the cornea in lattice dystrophy is prone to frequent erosions and is a compromised epithelial barrier to invasion by microorganisms. Patients must be made aware of this fact and should seek attention at the earliest following any trivial trauma. Management of minor corneal abrasions in them should be directed at healing the epithelium with adequate lubricants and preventing infection with topical antibiotic prophylaxis
Time delay factor can be used as a key factor for preventing the outbreak of a disease—Results drawn from a mathematical study of a one season eco-epidemiological model
No full textChatterjee and Chattopadhyay [Role of migratory bird population in an simple eco-epidemiological model, Math. Comp. Model. Dyn. Syst., in press] proposed and analyzed a one season eco-epidemiological model of susceptible and infective prey together with their predators. In such systems, time lags due to the gestation of the infective prey are of importance. In this paper we modify and analyze their model by taking this factor into consideration. Our analysis shows that the outbreak of the disease can be controlled by a careful and suitable increment of the time lag factor. Moreover, to preserve the stability of the coexisting equilibrium, the time lag factor plays an important role. To substantiate our analytical results, extensive numerical simulations are performed for a hypothetical set of parameter values
ROLE OF MIGRATORY BIRDS UNDER ENVIRONMENTAL FLUCTUATION — A MATHEMATICAL STUDY
No full textChatterjee and Chattopadhyay1 proposed and analyzed a simple one season eco-epidemiological model to understand the role of migratory birds in an eco-epidemiological scenario. In this paper, we have modified their model taking into account standard incidence as horizontal incidence. We have studied the proposed model both in the absence and in the presence of environmental disturbances. From our analysis, we observe that in the absence of the environmental fluctuations, the disease spread by migratory birds may be controlled by either decreasing the contact rate, or increasing the recovery or predation rates. Further, we also observe that if the artificial eutrophication (or intensity of white noise) is kept under a certain threshold value, the control procedure proposed in the deterministic case is also valid in the presence of environmental disturbances
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