Estimation of introduction and transmission rates of SARS-CoV-2 in a prospective household study

Household studies provide an efficient means to study transmission of infectious diseases, enabling estimation of susceptibility and infectivity by person-type. A main inclusion criterion in such studies is usually the presence of an infected person. This precludes estimation of the hazards of pathogen introduction into the household. Here we estimate age- and time-dependent household introduction hazards together with within household transmission rates using data from a prospective household-based study in the Netherlands. A total of 307 households containing 1,209 persons were included from August 2020 until March 2021. Follow-up of households took place between August 2020 and August 2021 with maximal follow-up per household mostly limited to 161 days. Almost 1 out of 5 households (59/307) had evidence of an introduction of SARS-CoV-2. We estimate introduction hazards and within-household transmission rates in our study population with penalized splines and stochastic epidemic models, respectively. The estimated hazard of introduction of SARS-CoV-2 in the households was lower for children (0-12 years) than for adults (relative hazard: 0.62; 95%CrI: 0.34-1.0). Estimated introduction hazards peaked in mid October 2020, mid December 2020, and mid April 2021, preceding peaks in hospital admissions by 1-2 weeks. Best fitting transmission models included increased infectivity of children relative to adults and adolescents, such that the estimated child-to-child transmission probability (0.62; 95%CrI: 0.40-0.81) was considerably higher than the adult-to-adult transmission probability (0.12; 95%CrI: 0.057-0.19). Scenario analyses indicate that vaccination of adults can strongly reduce household infection attack rates and that adding adolescent vaccination offers limited added benefit.

Estimation of introduction and transmission rates of SARS-CoV-2 in a prospective household study

Household studies provide an efficient means to study transmission of infectious diseases, enabling estimation of individual susceptibility and infectivity. A main inclusion criterion in such studies is often the presence of an infected person. This precludes estimation of the hazards of pathogen introduction into the household. Here we use data from a prospective household-based study to estimate SARS-CoV-2 age- and time-dependent household introduction hazards together with within household transmission rates in the Netherlands from August 2020 to August 2021. Introduction hazards and within-household transmission rates are estimated with penalized splines and stochastic epidemic models, respectively. The estimated hazard of introduction of SARS-CoV-2 in the households was lower for children (0-12 years) than for adults (relative hazard: 0.62; 95%CrI: 0.34-1.0). Estimated introduction hazards peaked in mid October 2020, mid December 2020, and mid April 2021, preceding peaks in hospital admissions by 1-2 weeks. The best fitting transmission models include increased infectivity of children relative to adults and adolescents, such that the estimated child-to-child transmission probability (0.62; 95%CrI: 0.40-0.81) was considerably higher than the adult-to-adult transmission probability (0.12; 95%CrI: 0.057-0.19). Scenario analyses show that vaccination of adults could have strongly reduced infection attack rates in households and that adding adolescent vaccination would have offered limited added benefit.

The impact of variant and vaccination on SARS-CoV-2 symptomatology; three prospective household cohorts

OBJECTIVES

We compared age-stratified SARS-CoV-2 symptomatology of wild-type/Alpha vs Omicron BA.1/BA.2 variant infected individuals and the impact of COVID-19 booster vaccination on Omicron symptom burden.

METHODS

Data from three European prospective household cohorts were used (April 2020 to April 2021 and January to March 2022). Standardized outbreak protocols included (repeated) polymerase chain reaction testing, paired serology, and daily symptom scoring for all household members. Comparative analyses were performed on 346 secondary household cases from both periods.

RESULTS

Children <12 years (all unvaccinated) experienced more symptoms and higher severity scores during Omicron compared with wild-type/Alpha period (P ≤0.01). In adults, Omicron disease duration and severity were reduced (P ≤ 0.095). Omicron was associated with lower odds for loss of smell or taste (adjusted odds ratio [aOR]: 0.14; 95% CI 0.03-0.50) and higher but non-significant odds for upper respiratory symptoms, fever, and fatigue (aORs: 1.85-2.23). No differences were observed in disease severity or duration between primary vs booster series vaccinated adults (P ≥0.12).

CONCLUSION

The Omicron variant causes higher symptom burden in children compared with wild-type/Alpha and lower in adults, possibly due to previous vaccination. A shift in symptoms occurred with reduction in loss of smell/taste for Omicron. No additional effect of booster vaccination on Omicron symptom burden was observed.

Longitudinal Household Assessment of Respiratory Illness in Children and Parents During the COVID-19 Pandemic

IMPORTANCE

In the early COVID-19 pandemic, SARS-CoV-2 testing was only accessible and recommended for symptomatic persons or adults. This restriction hampered assessment of the true incidence of SARS-CoV-2 infection in children as well as detailed characterization of the SARS-CoV-2 disease spectrum and how this spectrum compared with that of other common respiratory illnesses.

OBJECTIVE

To estimate the community incidence of SARS-CoV-2 infection in children and parents and to assess the symptoms and symptom severity of respiratory illness episodes involving SARS-CoV-2-positive test results relative to those with SARS-CoV-2-negative test results.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study randomly selected Dutch households with at least 1 child younger than 18 years. A total of 1209 children and adults from 307 households were prospectively followed up between August 25, 2020, and July 29, 2021, covering the second and third waves of the COVID-19 pandemic. Participation included SARS-CoV-2 screening at 4- to 6-week intervals during the first 23 weeks of participation (core study period; August 25, 2020, to July 29, 2021). Participants in all households finishing the core study before July 1, 2021, were invited to participate in the extended follow-up and to actively report respiratory symptoms using an interactive app until July 1, 2021. At new onset of respiratory symptoms or a SARS-CoV-2 positive test result, a household outbreak study was initiated, which included daily symptom recording, repeated polymerase chain reaction testing (nose-throat swabs and saliva and fecal samples), and SARS-CoV-2 antibody measurement (paired dried blood spots) in all household members. Outbreaks, households, and episodes of respiratory illness were described as positive or negative depending on SARS-CoV-2 test results. Data on participant race and ethnicity were not reported because they were not uniformly collected in the original cohorts and were therefore not representative or informative.

EXPOSURES

SARS-CoV-2-positive and SARS-CoV-2-negative respiratory illness episodes.

MAIN OUTCOMES AND MEASURES

Age-stratified incidence rates, symptoms, and symptom severity for SARS-CoV-2-positive and SARS-CoV-2-negative respiratory illness episodes.

RESULTS

Among 307 households including 1209 participants (638 female [52.8%]; 403 [33.3%] aged <12 years, 179 [14.8%] aged 12-17 years, and 627 [51.9%] aged ≥18 years), 183 household outbreaks of respiratory illness were observed during the core study and extended follow-up period, of which 63 (34.4%) were SARS-CoV-2 positive (59 outbreaks [32.2%] during the core study and 4 outbreaks [2.2%] during follow-up). SARS-CoV-2 incidence was similar across all ages (0.24/person-year [PY]; 95% CI, 0.21-0.28/PY). Overall, 33 of 134 confirmed SARS-CoV-2 episodes (24.6%) were asymptomatic. The incidence of SARS-CoV-2-negative respiratory illness episodes was highest in children younger than 12 years (0.94/PY; 95% CI, 0.89-0.97/PY). When comparing SARS-CoV-2-positive vs SARS-CoV-2-negative respiratory illness episodes in children younger than 12 years, no differences were observed in number of symptoms (median [IQR], 2 [2-4] for both groups), symptom severity (median [IQR] maximum symptom severity score, 6 [4-9] vs 7 [6-13]), or symptom duration (median [IQR], 6 [5-12] days vs 8 [4-13] days). However, among adults, SARS-CoV-2-positive episodes had a significantly higher number (median [IQR], 6 [4-8] vs 3 [2-4]), severity (median [IQR] maximum symptom severity score, 15 [9-19] vs 7 [6-11]), and duration (median [IQR] 13 [8-29] days vs 5 [3-11] days; P < .001 for all comparisons) of symptoms vs SARS-CoV-2-negative episodes.

CONCLUSIONS AND RELEVANCE

In this cohort study, during the first pandemic year when mostly partial or full in-person learning occurred, the SARS-CoV-2 incidence rate in children was substantially higher than estimated from routine testing or seroprevalence data and was similar to that of adult household members. Unlike in unvaccinated adults, SARS-CoV-2 symptoms and symptom severity in children were similar to other common respiratory illnesses. These findings may prove useful when developing pediatric COVID-19 vaccine recommendations.

Transmission of SARS-CoV-2 within households: a remote prospective cohort study in European countries

Household transmission studies are useful to quantify SARS-CoV-2 transmission dynamics. We conducted a remote prospective household study to quantify transmission, and the effects of subject characteristics, household characteristics, and implemented infection control measures on transmission. Households with a laboratory-confirmed SARS-CoV-2 index case were enrolled < 48 h following test result. Follow-up included digitally daily symptom recording, regular nose-throat self-sampling and paired dried blood spots from all household members. Samples were tested for virus detection and SARS-CoV-2 antibodies. Secondary attack rates (SARs) and associated factors were estimated using logistic regression. In 276 households with 920 participants (276 index cases and 644 household members) daily symptom diaries and questionnaires were completed by 95%, and > 85% completed sample collection. 200 secondary SARS-CoV-2 infections were detected, yielding a household SAR of 45.7% (95% CI 39.7–51.7%) and per-person SAR of 32.6% (95%CI: 28.1-37.4%). 126 (63%) secondary cases were detected at enrollment. Mild (aRR = 0.57) and asymptomatic index cases (aRR = 0.29) were less likely to transmit SARS-CoV-2, compared to index cases with an acute respiratory illness (p = 0.03 for trend), and child index cases (< 12 years aRR = 0.60 and 12-18 years aRR = 0.85) compared to adults (p = 0.03 for trend). Infection control interventions in households had no significant effect on transmission. We found high SARs with the majority of transmissions occuring early after SARS-CoV-2 introduction into the household. This may explain the futile effect of implemented household measures. Age and symptom status of the index case influence secondary transmission. Remote, digitally-supported study designs with self-sampling are feasible for studying transmission under pandemic restrictions.

Responsiveness of the glucocorticoid-suppressed pituitary-adrenocortical system of pigeons (Columba livia domestica) to stimulation with arginine vasopressin

This paper reports on the duration of the suppressive effects of single high and low doses of dexamethasone, cortisol, and prednisolone on the pituitary-adrenocortical (PA) system in pigeons. In addition, the effects of long-term daily administration of a high dose of dexamethasone are reported. In Expt. 1, low and high doses of dexamethasone (0.5 microgram/kg and 0.5 mg/kg), cortisol (15 micrograms/kg and 1.5 mg/kg), and prednisolone (3.5 micrograms/kg and 3.5 mg/kg) were administered around the expected nadir (4 hr before the peak) of the diurnal plasma corticosterone concentration. The recovery of the PA system was investigated by measuring plasma corticosterone concentrations before and 30 min after arginine vasopressin (AVP) stimulation (10 micrograms/kg) around the expected peak of plasma corticosterone concentrations. In Expt. 2, one high dose of each of the three glucocorticoids was administered 4 hr before the peak, followed by AVP stimulation around the expected peak of plasma corticosterone concentrations each day for 3 days. In Expt. 3, the recovery of the PA system following long-term daily administration of 1 mg/kg dexamethasone was investigated by repeated stimulations with AVP after cessation of the treatment. The results of these experiments (I) confirm that the PA system of pigeons is very sensitive to the suppressive effects of dexamethasone, cortisol, and prednisolone in a dose-dependent manner, (II) demonstrate that after cessation of glucocorticoid treatment the response to AVP stimulation is restored earlier than basal corticosterone concentrations, (III) demonstrate that after long-term glucocorticoid treatment the responsiveness of the PA system recovers relatively fast, and (IV) demonstrate that long-term treatment with a high dose of dexamethasone not only results in complete suppression of the PA system but is also a serious risk for infection and death.

No evidence for diurnal variation in the responsiveness of the pituitary-adrenocortical axis of the pigeon (Columba livia domestica) to stimulation with adrenocorticotrophin and vasopressin

The responsiveness of the pituitary-adrenocortical axis of the pigeon (Columba livia domestica) to intravenous administration of high and low doses of adrenocorticotrophic hormone (ACTH) and following arginine vasopressin (AVP) was investigated at two different moments of the diurnal rhythm. Administrations of ACTH and AVP were performed at the moment of low plasma corticosterone concentration and during high plasma corticosterone concentration. Plasma corticosterone concentrations following administration of AVP and ACTH did not change with the time of the day. It is concluded that for the assessment of pituitary adrenocortical function in pigeons the pituitary adrenocortical stimulation tests with AVP and ACTH can be used at any time of day.

Sensitivity of the hypothalamic-pituitary-adrenal system of pigeons (Columba livia domestica) to suppression by dexamethasone, cortisol, and prednisolone

The sensitivity of the hypothalamic-pituitary-adrenal system in pigeons (Columba livia domestica) to glucocorticoid feedback was studied after single intravenous administration of dexamethasone (500, 100, 50, 10, 5, 1, 0.5, and 0.1 micrograms/kg), cortisol (15,000, 3000, 1500, 300, 150, 30, 15, and 3 micrograms/kg), and prednisolone (3500, 700, 350, 70, 35, 7, 3.5, 0.7, and 0.35 micrograms/kg). Dose responses, the threshold doses, and the onset of maximum suppression were determined by measuring plasma corticosterone concentrations around the expected peak of plasma corticosterone in pigeons kept on a shifted-light regimen. At 52 hr following the highest dose of dexamethasone, and at 48 hr following the highest doses of cortisol and prednisolone, plasma corticosterone concentrations were similar to the initial values and to the control values. Following the minimum doses that resulted in suppression of the normal diurnal variation in plasma corticosterone concentration (0.5 microgram dexamethasone/kg, 15 micrograms cortisol/kg, and 0.7 microgram prednisolone/kg), plasma corticosterone concentrations were similar to values of the control group and to initial values within 24 hr. The onset of suppression of plasma corticosterone concentrations was between 30 and 60 min following 1 microgram dexamethasone/kg, 7 micrograms prednisolone/kg, or 30 micrograms cortisol/kg. Suppression was greatest at 60 min following prednisolone and cortisol administration, and at 90 min following dexamethasone administration. It is concluded that the hypothalamic-pituitary-adrenal system of pigeons reacts to exogenous glucocorticoids by early delayed feedback, is more sensitive to suppression by glucocorticoids than that of mammals, and is suppressed for the longest time by dexamethasone. These observations indicate that some of the side effects of glucocorticoid therapy are likely to be at least as frequent and as severe in birds as in mammals.

Diurnal rhythms of plasma corticosterone concentrations in racing pigeons (Columba livia domestica) exposed to different light regimens, and the influence of frequent blood sampling

The effects of two different light regimens and the frequency of blood sampling on the diurnal plasma corticosterone concentrations in racing pigeons (Columba livia domestica) were investigated. The daily light regimens tested were a period of light during the day (DL; lights on 0515-2215) and shifting of the light period by 12 hours (SL; lights on 1715-1015). In the first experiment, the influence of the frequency of blood sampling was investigated by comparing plasma corticosterone concentrations at 28-hr intervals for several days and at 4-hr intervals during one day. Sampling at 4-hr intervals resulted in significantly higher corticosterone concentrations in plasma than sampling at 28-hr intervals. Within both groups, the plasma corticosterone concentrations at the first and last sampling times did not differ significantly. Concentrations of plasma corticosterone were always highest during the dark period, and the corticosterone rhythm in the SL experiment was strictly in phase with the altered light/dark schedule.

[A field study of the efficacy of ivermectin in propylene glycol in the treatment of mange in guinea pigs]

The clinical manifestation of mange in a guinea-pig population in Utrecht is discussed. The etiology and the treatment with two subcutaneous injections of ivermectin 0.2 mg/kg with a ten-day interval, is described. A total of 37 guinea-pigs with symptoms and 36 guinea-pig without signs of mange were treated. On the 21st day all previously infested guinea-pigs were free of symptoms. During this study side-effects occurred in 11 of the 73 animals. The most prominent side-effects were a (sub-)dermal necrosis in the younger animals and an inflammation of the cutis in the older animals. The side-effects were probably caused by propylene glycol which was used as a diluent.

In vivo studies on the effects of ovine corticotrophin-releasing hormone, arginine vasotocin, arginine vasopressin, and haloperidol on adrenocortical function in the racing pigeon (Columba livia domestica)

This study investigates the effects of in vivo administration of pituitary stimulants in racing pigeons (Columba livia domestica). Plasma corticosterone concentrations were measured following intravenous administration of ovine corticotrophin-releasing hormone (oCRH) (0.1, 1, 10, and 100 micrograms/kg), arginine vasopressin (AVP) (0.01, 0.1, 1, and 10 micrograms/kg), arginine vasotocin (AVT) (0.01, 0.1, 1, and 5 micrograms/kg), and haloperidol (0.05, 0.5, and 5 micrograms/kg). Compared with mammals the pituitary-adrenocortical system of the pigeon appeared to be less sensitive to stimulation with oCRH, although high doses were well tolerated and gave a clear response. Both AVP and AVT stimulated corticosterone secretion, AVT in a more pronounced dose-dependent manner than AVP. The natural neurohypophysial peptide in birds, AVT, was less well tolerated in high doses than AVP. The clear response to haloperidol indicates that the hypothalamo-pituitary-adrenocortical system is under dopaminergic inhibition. Of the pituitary stimulants tested AVP (10 micrograms/kg) and oCRH (100 micrograms/kg) are the most appropriate for testing the integrity of the pituitary-adrenocortical system in the pigeon.

Diseases in parrots

This article can be regarded as a primer to psittacine medicine. An introduction to pet psittacine species and Dutch legislation with regard to keeping parrots as pets, is followed by diagnostic techniques. Some emergency therapeutic measures are highlighted. A review is presented of some characteristic or important parrot diseases.

[Lethal effects of various antimicrobial agents and clinically usable alternatives in rabbits and rodents]

The lethal effects of antibiotics which may be observed in rabbits and some rodent species are reviewed. A selection of antibiotics and chemotherapeutic agents and their respective dosages are referred to, which may be used therapeutically in these animals. Suggestions are made for the treatment of enterocolitis induced by antibiotics in rabbits.

Blood chemistry for the diagnosis of hepatobiliary disease in birds. A review

A review is presented of current knowledge with regard to blood chemistry for the diagnosis of hepatobiliary disease in birds. Straightforward conclusions are difficult, because research on this subject has been limited. Jaundice caused by hyperbilirubinaemia occurs infrequently in birds, because the main bile pigment is biliverdin and not bilirubin. A yellow discolouration of avian plasma is often caused by the presence of carotenoids. The diagnostic value of plasma ALAT concentrations is controversial. Although ASAT and LD are not specific for the liver they appear to be sensitive enzymes to detect liver cell damage. GLDH is liver specific in a number of animal species (including birds) and might prove to be a useful enzyme for diagnostic purposes. AP and GGT seem less useful. Little information is available on the diagnostic value of plasma bile acids and plasma dye clearance tests.