Models of superinfection and acquired immunity to multiple parasite strains

1996 ◽  
Vol 33 (04) ◽  
pp. 915-932 ◽  
Author(s):  
P. J. M. Milligan ◽  
D. Y. Downham
Keyword(s):  
Control Measures ◽  
Older Individuals ◽  
Close Approximation ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Duration Of Infection ◽  
Bivariate Poisson Distribution ◽  
Vector Borne ◽  
The Mean ◽  
Different Strains

Individuals in communities in which different strains of pathogen are circulating can acquire resistance by accumulating immunity to each strain. After considering susceptibility, models of infection and immunity are defined for vector-borne diseases such as malaria and trypanosomiasis. For these models the prevalence of infection, the number of infections per individual, and the mean duration of infection, increase rapidly in young individuals, but decrease in older individuals as immunity is acquired to the various strains of pathogen; the mean interval between successive infections lengthens with age. The bivariate Poisson distribution is shown to be a close approximation to some stochastic processes. The models explain observed cross-sectional patterns of age prevalence, and longitudinal patterns in which individuals typically continue to become infected as they age, albeit with decreasing frequency. In these models the time spent infected depends on parasite diversity, as well as the inoculation and recovery rates. It is shown that control measures can cause an increase in the number of infections and the prevalence of infection in older individuals, and in the average prevalence in the community, even when strain-specific immunity is life-long.

Models of superinfection and acquired immunity to multiple parasite strains

1996 ◽  
Vol 33 (4) ◽  
pp. 915-932 ◽  
Author(s):  
P. J. M. Milligan ◽  
D. Y. Downham
Keyword(s):  
Control Measures ◽  
Older Individuals ◽  
Close Approximation ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Duration Of Infection ◽  
Bivariate Poisson Distribution ◽  
Vector Borne ◽  
The Mean ◽  
Different Strains

Individuals in communities in which different strains of pathogen are circulating can acquire resistance by accumulating immunity to each strain. After considering susceptibility, models of infection and immunity are defined for vector-borne diseases such as malaria and trypanosomiasis. For these models the prevalence of infection, the number of infections per individual, and the mean duration of infection, increase rapidly in young individuals, but decrease in older individuals as immunity is acquired to the various strains of pathogen; the mean interval between successive infections lengthens with age. The bivariate Poisson distribution is shown to be a close approximation to some stochastic processes. The models explain observed cross-sectional patterns of age prevalence, and longitudinal patterns in which individuals typically continue to become infected as they age, albeit with decreasing frequency. In these models the time spent infected depends on parasite diversity, as well as the inoculation and recovery rates. It is shown that control measures can cause an increase in the number of infections and the prevalence of infection in older individuals, and in the average prevalence in the community, even when strain-specific immunity is life-long.

scholarly journals Issues on Vector Related Diseases Transmission: People's Perception & Practices

2019 ◽  
Vol 10 (1) ◽  
pp. 32-37
Author(s):  
Md Mahfuzar Rahman ◽  
Md Atiqur Rahman ◽  
Rizona Jnui ◽  
Abu Kawser ◽  
Khalid Omar Shahin
Keyword(s):  
Vector Control ◽  
Public Awareness ◽  
Sampling Technique ◽  
Cross Sectional Study ◽  
Control Measures ◽  
Health Concern ◽  
Mosquito Net ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Vector Borne

Background: The vector borne diseases pose an immense public health concern and also a growing urban and rural problem. The aim of this study was to findout the perception and practices among the rural households regarding vector related diseases in some selected villages of Dhamrai Upazila. Material and Methods: This descriptive cross sectional study was carried out among 1380 respondents by purposive sampling technique during the period from 6th to 8th January, 2018 in different villages of Dhamrai Upazila, Dhaka.. Results: Then study revealed that majority of the respondents 89% were Muslims by religion and about 65% respondents were found within the age 25-55 years. (mean age 37.81±14.72 years). Out of 1380 respondents, majority 87% & 86% mentioned Mosquitos and Houseflies as vectors transmitting the diseases followed by 48% Itch mite, 45% Louse and 27% Sandflies. About 85% & 88% mentioned Malaria & Dengue fever transmitted by vectors followed by 58% Chikungunya, 42% Kala azar, 13% Filariasis and 44% Typhoid fever. However, 71%, 83%, 59% & 3% respondents mentioned Mosquito bite as the mode of transmission of Malaria, Chikungunya and Filariasis respectively. About 88%, 75%, 44% and 39% respondents mentioned Personal protection, Avoidance of water collection, Fogging and Insecticidal spraying as the vector control measures. Nevertheless, 92%, 81% and 30% respondents are found practiced Mosquito net, Mosquito coil and Screening of windows as their usual vector control measures. Conclusion: In this study community awareness in terms of perceptions, knowledge and practices regarding vector borne diseases are found deficient. There should be intensified efforts in promoting personal protective measures through creating public awareness towards prevention of vector borne diseases in the locality. Anwer Khan Modern Medical College Journal Vol. 10, No. 1: Jan 2019, P 32-37

scholarly journals Resilience and vulnerability of maternity services in Zimbabwe: a comparative analysis of the effect of Covid-19 and lockdown control measures on maternal and perinatal outcomes, a single-centre cross-sectional study at Mpilo Central Hospital

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Clare Shakespeare ◽  
Handsome Dube ◽  
Sikhangezile Moyo ◽  
Solwayo Ngwenya
Keyword(s):  
Perinatal Outcomes ◽  
Control Measures ◽  
Central Hospital ◽  
Cross Sectional ◽  
Maternity Services ◽  
Before And After ◽  
The Mean ◽  
Significant Change ◽  
The Impact ◽  
Mpilo Central Hospital

Abstract Background On the 27th of March 2020 the Zimbabwean government declared the Covid-19 pandemic a ‘national disaster’. Travel restrictions and emergency regulations have had significant impacts on maternity services, including resource stock-outs, and closure of antenatal clinics during the lockdown period. Estimates of the indirect impact of Covid-19 on maternal and perinatal mortality was expected it to be considerable, but little data was yet available. This study aimed to examine the impact of Covid-19 and lockdown control measures on non-Covid outcomes in a government tertiary level maternity unit in Bulawayo, Zimbabwe, by comparing maternal and perinatal morbidity and mortality before, and after the lockdown was implemented. Methods This was a retrospective, observational study, using a cross-sectional design to compare routine monthly maternal and perinatal statistics three months before and after Covid-19 emergency measures were implemented at Mpilo Central Hospital. Results Between January-March and April-June 2020, the mean monthly deliveries reduced from 747.3 (SD ± 61.3) in the first quarter of 2020 to 681.0 (SD ± 17.6) during lockdown, but this was not statistically significant, p = 0.20. The Caesarean section rates fell from a mean of 29.8% (SD ± 1.7) versus 28.0% (SD ± 1.7), which was also not statistically significant, p = 0.18. During lockdown, the percentage of women delivering at Mpilo Central Hospital who were booked at the hospital fell from a mean of 41.6% (SD ± 1.1) to 35.8% (SD ± 4.3) which was statistically significant, p = 0.03. There was no significant change, however, in maternal mortality or severe maternal morbidity (such as post-partum haemorrhage (PPH), uterine rupture, and severe preeclampsia/eclampsia), stillbirth rate or special care baby unit admission. There was an increase in the mean total number of early neonatal deaths (ENND) (mean 18.7 (SD ± 2.9) versus 24.0 (SD ± 4.6), but this was not statistically significant, p = 0.32. Conclusions Overall, maternity services at Mpilo showed resilience during the lockdown period, with no significant change in maternal and perinatal adverse outcomes, with the same number of man-hours worked before and during the lockdown Maternal and perinatal outcomes should continue to be monitored to assess the impact of Covid-19 and the lockdown measures as the pandemic in Zimbabwe unfolds. Further studies would be beneficial to explore women’s experiences and understand how bookings and deliveries at local clinics changed during this time.

Pre and post flooding malaria parasitemia in gravid women, South East, Nigeria

2021 ◽  
Vol 2 (5) ◽  
Author(s):  
Ekwebene OC ◽  
◽  
Obidile VC ◽  
Nnamani CP ◽  
Eleje GU ◽  
...  
Keyword(s):  
Climate Change ◽  
Pregnant Women ◽  
Health Care Professionals ◽  
Malaria Parasite ◽  
P Value ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Seasonal Flooding ◽  
Vector Borne ◽  
The Relationship

The effect of global change on the incidence of vector borne diseases including malaria is of great importance. Malaria has been regarded as one of the most sensitive disease that responds fast to climate change. Pregnant women tend to have reduced immunity are more vulnerable to vector borne diseases such as malaria especially with climate change like flooding where these vectors borne diseases are endemic. To measure malaria parasitaemia in gravid women pre and post flooding and also to determine the relationship between malaria and seasonal flooding in South east Nigeria. This was a hospital-based cross-sectional study involving pregnant women aged 15- 45 years attending the antenatal clinics of two maternity centres in a rural community South east Nigeria. Malaria was determined using the thick and thick blood films. Plasmodium falciparum species was examined in this study. Chi-square was used to assess the relationship between malaria and seasonal flooding. One Hundred and fifty pregnant women were recruited for the study. The prevalence of malaria in the gravid women pre and post flooding were 60.00% and 65.30% respectively. Malaria parasite was highest in the gravid women aged 28-31 years and the primigravids. There was no statistical difference between malaria and parity. The mean parasite density in the gravid women was significantly higher post flooding than pre flooding with p-value of 0.001. There was no significant relationship between malaria parasite in gravid women and the periods of investigation. The prevalence of malaria parasite among gravid women in the study area is high regardless of the seasonal flooding. Hence, the need for adherence to malaria prophylaxis protocol by the health care professionals and increase on community health education on malaria preventive strategies.

scholarly journals A comparative study on knowledge and perception of vector borne diseases among rural and urban population in Tamil Nadu

2019 ◽  
Vol 6 (6) ◽  
pp. 2672
Author(s):  
Roselin V. ◽  
Srisanthanakrishnan V.
Keyword(s):  
Urban Population ◽  
Tamil Nadu ◽  
Community Education ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Vector Borne Disease ◽  
Rural And Urban ◽  
Vector Borne ◽  
Knowledge And Practice

Background: Vector-borne diseases (VBD) remain a major public health challenge, in India. Knowledge about VBD, social, demographic and environmental factors strongly influence the vector transmission and results in major outbreaks. Hence this study was conducted to assess knowledge and practice along with environmental conditions prevailing in both rural and urban areas.Methods: Cross sectional study was conducted in rural and urban field practice area of Sri Muthukumaran Medical College and Research Institute, Chennai, during June 2018 to December 2018. A total of 472 participants with 236 participants from each urban and rural area were included. Data was collected using proforma and analysis was done using SPSS 16.Results: Knowledge about VBD like dengue was 63.6% and 76.7% among rural and urban population, respectively. Similarly malaria was known by knows 59.3% and 68.2% of rural and urban participants. Japanese Encephalitis was the least known mosquito borne disease in both the groups. (p=0.0136). Common breeding sites addressed by the rural population were artificial collected water (36.9%) and urban population was dirty water (42.8%).Conclusions: Knowledge and practice of preventing vector borne disease is still lacking among both rural and urban participants. Spreading knowledge about VBD is a part in effective vector borne disease control which can be achieved by community education alone rather than insecticides and sprays.

scholarly journals THE IMPACT OF GLOBAL WARMING ON THE PUBLIC HEALTH INCREASING THE BACTERIAL CAUSING INFECTIOUS DISEASES PERFORMED BY EXPERIMENT: VECTOR-BORNE DISEASES INSECTS, TAIF, KSA

2017 ◽  
Vol 5 (5) ◽  
pp. 42-53
Author(s):  
Sherifa Mostafa M. Sabra ◽  
Samar Ahamed
Keyword(s):  
Public Health ◽  
Global Warming ◽  
Infectious Diseases ◽  
Vector Borne Diseases ◽  
The Public ◽  
Colony Forming Unit ◽  
Tapinoma Sessile ◽  
Vector Borne ◽  
The Mean ◽  
The Impact

The search conducted on "The impact of global warming (GW) on the public health (PH) increasing the bacterial causing infectious diseases (IDs) performed by experiment: Vector-borne diseases (VBDs) insects, Taif, KSA", the experiment used ants (Taif Tapinoma sessile), prepared, arranged appropriate nests and adjusted the temperature at (20, 25, 30, 35, 40 and 45°C), for a week of each zone. It revealed the behaviour as (normal, semi-normal and ab-normal), the mean of mortality rates were between (0-53.3%). The bacterial contents measured by the turbidity indicated the presence of multiplication, were between (0.109-0.328). The bacterial growth degrees by sings were between (+ - +++++) and percent between (12-100%). Colony Forming Unit/ml (CFU/ml) confined between (1.8X102-15.0X102)/mL. Through this experiment it turned out the GW had a significant role on the PH, helped the proliferation of bacterial pathogens that caused IDS. The conclusion wiped from the experiment that the extent degrees of GW disadvantages on the PH. The PH workers must take the "Preventive Health Prophylaxis Measures" (PHPMs) to protect the individuals from IDs by eliminating the VBDs of various types, monitoring the immunological situation of individuals, provided the vaccinations of IDs and preparing for complete PHPMs against any changes in the PH.

Cross-sectional survey of health management and prevalence of vector-borne diseases, endoparasites and ectoparasites in Samoan dogs

2017 ◽  
Vol 95 (12) ◽  
pp. 462-468 ◽  
Author(s):  
RJ Carslake ◽  
KE Hill ◽  
K Sjölander ◽  
SF Hii ◽  
D Prattley ◽  
...  
Keyword(s):  
Health Management ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Vector Borne

scholarly journals Infectivity titrations of myxoma virus in the rabbit and the developing chick embryo

1956 ◽  
Vol 54 (2) ◽  
pp. 246-257 ◽  
Author(s):  
Frank Fenner ◽  
G. A. McIntyre
Keyword(s):  
Chorioallantoic Membrane ◽  
Myxoma Virus ◽  
Close Approximation ◽  
Rabbit Skin ◽  
Maximum Value ◽  
Average Probability ◽  
Proportional Relationship ◽  
The Mean ◽  
Different Strains ◽  
Infectious Unit

Titrations of the same preparations of myxoma virus have been made on the chorioallantoic membranes of developing chick embryos and by the intradermal inoculation of rabbits. Six strains of widely differing virulence for the rabbit were used.No differences were found in the infectivity of different strains for either the rabbit or the egg, even though the severity of the symptoms produced in the rabbit varied greatly with different strains; and although some had never previously been inoculated in eggs and one had been subjected to seventy-five serial passages on the chorioallantoic membrane.The egg was less sensitive than the rabbit, the mean number of infections per dose for rabbits relative to eggs being 2.46, taken over all strains. This ratio did not differ significantly between strains of myxoma virus.There was evidence of some host variation in rabbit susceptibility and a great deal of variation in egg susceptibility. The maximum value for the average probability that an infectious unit would produce a lesion in the rabbit skin was about 0.6, and the maximum value for the average probability that an infectious unit would produce a pock on the chorioallantoic membrane was 0.25.Titration of several closely spaced dilutions of different strains of the virus on the chorioallantoic membrane showed a reasonably close approximation to a proportional relationship between the pock count and the virus dilution. The change with dilution in the proportion of failures to infect rabbits approximated to expectation. Both lines of evidence are consistent with the hypothesis that a pock or skin lesion is initiated by one infective unit of virus, and that the infective unit is stable with dilution.

scholarly journals Endoparasites and vector-borne pathogens in dogs from Greek islands: pathogen distribution and zoonotic implications

2018 ◽  
Author(s):  
Anastasia Diakou ◽  
Angela Di Cesare ◽  
Simone Morelli ◽  
Mariasole Colombo ◽  
Lenaig Halos ◽  
...  
Keyword(s):  
Linear Models ◽  
Clinical Signs ◽  
Rhipicephalus Sanguineus ◽  
Toxocara Canis ◽  
Control Measures ◽  
Rickettsia Conorii ◽  
Vector Borne Diseases ◽  
Vector Borne ◽  
Endemic Areas ◽  
Of Greece

AbstractThe present study investigated the presence of endo- and ecto-parasites, and vector-borne pathogens, in dogs from four islands of Greece. A total of 200 owned and sheltered dogs were examined with different microscopic, serological and molecular methods.Of the examined dogs, 130 (65%) were positive for one or more parasites and/or vector-borne pathogens. The most common zoonotic intestinal helminths recorded were Ancylostomatidae (12.5%) and Toxocara canis (3.5%). Ninety-three dogs (46.5%) seroreacted to Rickettsia conorii. Twenty-two (11%) of them were also PCR positive and 7 (3.5%) showed corpuscoles suggestive of Rickettsia spp. on the blood smears. Nineteen dogs (9.5%) were seropositive for Ehrlichia canis, three of them being also PCR positive. Dogs positive for Anaplasma phagocytophilum-Anaplasma platys (1%), Dirofilaria immitis (0.5%) and Babesia canis (0.5%) were also found. Fleas and ticks were recorded in 53 (26.5%) and 50 (25%) dogs and all specimens were identified as Ctenocephalides felis felis and Rhipicephalus sanguineus sensu latu. Binary multiple univariate Generalized Linear Models were used to investigate factors and clinical signs related to the recorded positivity, while the association of specific signs with the pathogens was evaluated using tests of independence. Knowledge of occurrence and impact of zoonotic parasites and vector-borne pathogens in dog populations is crucial to prevent the infection in animals and people, and to control the risk of spreading of these pathogens in endemic and non-endemic areas.Author summaryBoth owned and sheltered dogs can harbor a variety of intestinal and extra-intestinal endoparasites, as well as vector-borne pathogens and ectoparasites, of zoonotic concern. Dog shelters and stray dogs are present in several touristic areas of Greece, including Sporades and Cyclades islands, where tourists often bring their pets with them, likely travelling from non-endemic to endemic areas. The present study has been carried out with the aim to evaluate the occurrence of the aforementioned pathogens. Data obtained showed that they are present in canine populations of Greece, with possibilities of infection for travelling dogs, which can also contribute to the spreading of zoonotic vector-borne diseases, introducing new pathogens in previously non-endemic areas. For these reasons, a constant monitoring of the epidemiological situation, improving control measures and correct diagnostic approaches are of primary importance for the prevention of canine and human infections, decreasing the spreading of potentially deadly pathogens.

scholarly journals Prevalence of atrial fibrillation in patients taking TSH suppression therapy for management of thyroid cancer

2012 ◽  
Vol 35 (3) ◽  
pp. 152 ◽  
Author(s):  
Abdulgani Abonowara ◽  
Ata Quraishi ◽  
John L. Sapp ◽  
Mohammed H. Alqambar ◽  
Adi Saric ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Thyroid Cancer ◽  
Suppressive Therapy ◽  
Background Suppression ◽  
Published Data ◽  
Older Individuals ◽  
Cross Sectional ◽  
Tsh Suppression ◽  
Tsh Suppression Therapy ◽  
The Mean

Background: Suppression of thyroid stimulating hormone (TSH) below the normal range with administration of L-thyroxine has been shown to improve survival in patients treated for thyroid cancer (TC). Although most TC patients require long-term TSH suppression therapy, the effect of this treatment on cardiac rhythm remains unknown. A cross-sectional study was conducted to determine the prevalence of atrial fibrillation (AF) in TC patients on TSH suppressive therapy. Methods: All TC patients seen between June 2009 and March 2010 through a multidisciplinary thyroid oncology clinic, Halifax, Nova Scotia, Canada, for whom TSH suppressive therapy had previously been recommended, were recruited into the study. Each patient underwent an electrocardiogram and filled out a questionnaire relevant to causes, signs/symptoms of AF and/or its complications. The prevalence of AF in this population then was compared against the published prevalence of AF in general populations. Results: A total of 351 patients were seen in the thyroid clinic of which 136 patients met the inclusion criteria for the study. The mean age was 52 years, 85% were female, and mean follow-up duration prior to recruitment was 11 years. The mean TSH was 0.17 mIU/L (Normal: 0.35 – 5.5 mIU/L). There were 14 patients found to have AF (two patients had long-standing persistent AF and 12 patients had paroxysmal AF). The mean ages of patients with and without AF were 61.6 years and 51.4 years, respectively (P = 0.01). Prevalence of AF in the study group was 10.3%; the rate of AF in the TC patients aged 60 years and over (17.5%) was higher than the rate of AF in published data in people 60 years and over (P < 0.001). AF was diagnosed after the initiation of the TSH suppression therapy in all except one patient. Conclusion: TSH suppression in thyroid cancer is associated with a high prevalence of AF, particularly in older individuals.

Sign in / Sign up

Export Citation Format

Share Document