Time patterns of precautionary health behaviours during an easing phase of the COVID-19 pandemic in Europe

Using data from the COVID-19 questionnaire of the Survey of Health, Ageing and Retirement in Europe (SHARE), we investigate the time patterns of precautionary health behaviours of individuals aged 50 years and above during the summer of 2020, an easing phase of the COVID-19 pandemic in Europe. We also examine how these health behaviours differ by the presence of chronic conditions such as hypertension, high cholesterol level, heart disease, diabetes or chronic bronchitis, which can be considered as risk factors for COVID-19. Our results suggest that while on average, people became less precautious during the analysed time period, this is less so for those who are at higher risk. We also document large regional differences in precautionary health behaviours and show that higher-risk individuals are on average more cautious in all regions. We conclude that people adjusted their health behaviours in line with the generally understood risk of the COVID-19 disease. At the same time, our results also point out divergences in the level of willingness to take different precautionary steps.

The effect of involuntary retirement on healthcare use

We analyze the causal effect of involuntary retirement on detailed indicators of healthcare use and mortality. We leverage a pension reform in Hungary which forced public sector workers above the statutory retirement age to full time retirement. Using rich administrative data, we find that on the 3-year horizon, involuntary retirement decreases the number of primary care doctor visits, the use of systemic antiinfectives and respiratory drugs, and the non-zero spending on antiinfectives, the drugs of the alimentary tract and metabolism and of the cardiovascular system. The impact on the latter two drug categories is driven by the drop in income due to involuntary retirement. We conclude that there is little evidence for health deteriorating effects of involuntary retirement and discuss the possible mechanisms behind our results.

Income gradient of pharmaceutical panic buying at the outbreak of the COVID-19 pandemic

We analyze the timing, magnitude, and income dependence of pharmaceutical panic buying around the outbreak of the COVID-19 pandemic in Hungary. We use district-level monthly and daily administrative data on detailed categories of pharmaceutical purchases, merge them to income statistics, and estimate multilevel panel models. Our main results are as follows. First, the days of therapy (DOT) of pharmaceutical purchases increased by more than 30% in March 2020, when major lockdown measures were announced. This pattern holds for almost all categories of pharmaceuticals. Second, shortly after the panic reactions, the aggregate amount of pharmaceutical purchases returned to their preshock levels; however, the frequency of pharmacy visits decreased. Third, the panic buying reaction was significantly stronger in richer geographical areas, where-according to the daily data-people also reacted earlier to the pandemic-related news. Overall, the results suggest that panic buying of pharmaceuticals can have detrimental effects on vulnerable populations.

Caesarean delivery and the use of antidepressants

BACKGROUND

The high ratio of caesarean sections (C-sections) is a major public health issue in the developed world; but its implications on maternal mental health are not well understood.

METHODS

We use individual-level administrative panel data from Hungary between 2010 and 2016 to analyze the relationship between caesarean delivery and antidepressant consumption, an objective indicator of mental health. We focus on low-risk deliveries of mothers without subsequent birth in 3 years, and include around 135 000 observations.

RESULTS

After controlling for medical and socio-economic variables, antidepressant use before delivery is associated with an elevated risk of C-section (adjusted OR = 1.10, 95% CI 1.05-1.14) and C-section is associated with a higher probability of antidepressant use within 1-3 years after delivery (e.g. adjusted OR = 1.21, 95% CI 1.12-1.30, within 3 years after delivery, among mothers without pre-delivery antidepressant consumption). Our data restriction ensures that the results are not driven by a mechanical impact of decreasing fertility on the continuation of antidepressant use after a C-section.

CONCLUSIONS

The results suggest that C-section is associated with worse mental health over the 1- to 3-year horizon after birth. This relationship is particularly important if a caesarean delivery is not necessary due to medical reasons, and physicians as well as expectant mothers should be made aware of the potential mental health implications of the mode of delivery.

Regional differences in diabetes across Europe - regression and causal forest analyses

We examine regional differences in diabetes within Europe, and relate them to variations in socio-economic conditions, comorbidities, health behaviour and diabetes management. We use the SHARE (Survey of Health, Ageing and Retirement in Europe) data of 15 European countries and 28,454 individuals, who participated both in the 4th and 7th (year 2011 and 2017) waves of the survey. First, we estimate multivariate regressions, where the outcome variables are diabetes prevalence, diabetes incidence, and weight loss due to diet as an indicator of management. Second, we study the heterogeneous impact of demographic, socio-economic, health and lifestyle indicators on the regional differences in diabetes incidence with causal random forests. Compared to Western Europe, the odds of a new diabetes diagnosis over a six-year horizon is 2.2-fold higher in Southern and 2.6-fold higher in Eastern Europe. Adjusting for individual characteristics, the odds ratio decreases to 1.8 in the South-West and to 2.0 in the East-West dimension. These remaining differences are mostly explained by country-specific healthcare indicators. Based on the causal forest approach, the adjusted East-West difference is essentially zero for the lowest risk groups (tertiary education, employment, no hypertension, no overweight) and increases substantially with these risk factors, but the South-West difference is much less heterogeneous. The prevalence of diet-related weight loss around the time of diagnosis also exhibits regional variation. The results suggest that the regional differences in diabetes incidence could be reduced by putting more emphasis on diabetes prevention among high-risk individuals in Eastern and Southern Europe.

The closer the better: does better access to outpatient care prevent hospitalization?

In 2010-2012, new outpatient service locations were established in poor Hungarian micro-regions. We exploit this quasi-experiment to estimate the extent of substitution between outpatient and inpatient care. Fixed-effects Poisson models on individual-level panel data for years 2008-2015 show that the number of outpatient visits increased by 19% and the number of inpatient stays decreased by 1.6% as a result, driven by a marked reduction of potentially avoidable hospitalization (PAH) (5%). In our dynamic specification, PAH effects occur in the year after the treatment, whereas non-PAH only decreases with a multi-year lag. The instrumental variable estimates suggest that a one euro increase in outpatient care expenditures produces a 0.6 euro decrease in inpatient care expenditures. Our results (1) strengthen the claim that bringing outpatient care closer to a previously underserved population yields considerable health benefits, and (2) suggest that there is a strong substitution element between outpatient and inpatient care.

[Early experience with minimal invasive treatment of thirty-one thoracolumbar injury cases]

The authors report on their experience with minimal invasive treatment of thirtyone thoracolumbar injury cases. The medical charts, radiological documentation (preop CT and MRI scans, postop CT scans at 3 and 6 months) were analysed retrospectively. All pedicle screws were inserted appropriately, there was no neurological deterioration or surgical site infection postoperatively. There were three cases of radiological loss of correction, however, these were clinically irrelevant. There were no screw loosening or implant failure observed. According to our experience, which coincedes with literature data, this minimally invasive percutaneous pedicle screw technique can be recommended for the treatment of thoracolumbar injury.

How does retirement affect healthcare expenditures? Evidence from a change in the retirement age

Using individual-level administrative panel data from Hungary, we estimate causal effects of retirement on outpatient and inpatient care expenditures and pharmaceutical expenditures. Our identification strategy is based on an increase in the official early retirement age of women, using that the majority of women retire upon reaching that age. According to our descriptive results, people who are working before the early retirement age have substantially lower healthcare expenditures than nonworkers, but the expenditure gap declines after retirement. Our causal estimates from a two-part (hurdle) model show that the shares of women with positive outpatient care, inpatient care, and pharmaceutical expenditures, respectively, decrease by 3.0, 1.4, and 1.3 percentage points in the short run due to retirement. These results are driven by the relatively healthy, by those who spent some time on sick leave and by the less educated. The effect of retirement on the size of positive healthcare expenditures is generally not significant.

Implication of external price referencing and parallel trade on pharmaceutical expenditure: indirect evidence from lower-income European countries

External price referencing (EPR) is applied more and more frequently worldwide by payers to control pharmaceutical prices. Together with the parallel trade of pharmaceuticals, EPR may result in lower pharmaceutical prices in higher-income countries and higher prices in lower-income countries, which implies that pharmaceutical expenditure grows more rapidly in the latter than in the former group. Our objective was to assess this hypothesis. We used hierarchical linear models on country-level panel data to show that-after controlling for compounding factors such as GDP, the proportion of the old-age population or life expectancy-the annual growth rate of pharmaceutical expenditure was 2.1% points larger in the lower- than in the higher-income members of the European Union between 2000 and 2008. This difference in trends became non-significant (0.6% points) after the onset of the global economic crisis. There was no significant difference between lower- and higher-income countries in the growth rate of non-pharmaceutical health expenditure in either period. Our results indirectly support the presence of price convergence of pharmaceuticals among European countries, and EPR and parallel trade may provide a reasonable explanation to the observed trend difference of pharmaceutical expenditure in the two groups of countries between 2000 and 2008. This higher growth rate of pharmaceutical expenditure put extra burden on public health care budgets in lower-income countries and resulted in disproportionately more cost-containment measures compared to higher-income countries after 2008. It remains to be seen whether the disappearance of the difference in trend growth rates due to special health policy interventions in countries with economic difficulties is temporary or permanent.

Comparison of Clinical Symptoms and Magnetic Resonance Angiographic (MRA) Results in Patients with Trigeminal Neuralgia and Persistent Idiopathic Facial Pain. Medium-Term Outcome after Microvascular Decompression of Cases with Positive MRA Findings

To evaluate whether NC could be demonstrated preoperatively, high-resolution magnetic resonance angiography (MRA) was performed in 287 consecutive patients with TN and persistent idiopathic facial pain (PIFP) on a 0.5-T and a 1-T MR unit. Depending on the clinical symptoms, the TN cases were divided into typical TN and trigeminal neuralgia with non-neuralgic interparoxysmal pain (TNWIP) groups. Microvascular decompression (MVD) was performed in 103 of the MRA-positive cases. The patients were followed up postoperatively for from 1 to 10 years. The clinical symptoms were compared with the imaging results. The value of MRA was assessed on the basis of the clinical symptoms and surgical findings. The outcome of MVD was graded as excellent, good or poor. The clinical symptoms were compared with the type of vascular compression and the outcome of MVD. The MRA image was positive in 161 (56%) of the 287 cases. There were significant differences between the clinical groups: 66.5% of the typical TN group, 47.5% of the TNWIP group and 3.4% of the PIFP group were positive. The quality of the MR unit significantly determined the ratio of positive/negative MRA results. The surgical findings corresponded with the MRA images. Six patients from the MRA-negative group were operated on for selective rhizotomy and no NC was found. Venous compression of the trigeminal nerve was observed in a significantly higher proportion in the background of TNWIP than in that of typical TN on MRA imaging (24.1% and 0.8%, respectively) and also during MVD (31.2% and 1.2%, respectively). Four years following the MVD, 69% of the patients gave an excellent, 23% a good and 8% a poor result. The rate of some kind of recurrence of pain was 20% in the typical TN and 44% in TNWIP group. The rate of recurrence was 57% when pure venous compression was present. The only patient who was operated on from the PIFP group did not react to the MVD. The clinical symptoms and preoperative MRA performed by at least a 1-T MR unit furnish considerable information, which can play a role in the planning of the treatment of TN.

Effect of pre- and post-partum supplementation with lipid-encapsulated conjugated linoleic acid on milk yield and metabolic status in multiparous high-producing dairy cows

We evaluated the lactation performance, liver lipid content and plasma metabolites indicating the energy balance of dairy cows supplemented with conjugated linoleic acid (CLA) pre- and post-partum (PP) vs. only PP. A total of 60 cows were divided into three groups (n = 20). Daily diet of cows was supplemented with 14 g of CLA (7 g cis-9, trans-11 and 7 g trans-10, cis-12 isomers) from week 3 before the expected date of calving (group CLA1), or from the day of calving (group CLA2) until 77-91 days PP. Control cows were fed an isocaloric, isonitrogenous and isolipidic diet without CLA. Between week 3 and week 6 PP, the milk yield of cows in both CLA-treated groups was approximately 4.5 kg higher (p < 0.05) than in control. Milk fat concentrations decreased from week 3 and were lower in both CLA groups than in control (p < 0.01). Body condition score loss was lower (p < 0.05) in the CLA1 than in the control group on week 5 PP. By week 11 PP, the body condition of both CLA1 and CLA2 groups exceeded that of control. Plasma non-esterified fatty acid was lower in CLA1 compared to CLA2 and control during the early PP period (p < 0.05), while this difference faded away by the late PP period. Beta-hydroxybutyrate (BHBA) increased rapidly in all groups following calving. In CLA1 group, it began to decrease sooner than in CLA2 and control. The prevalence of subclinical ketosis (BHBA > 1.2 mm) was lower in CLA1 group than in CLA2 and control (p < 0.05). Liver biopsy analyses showed that CLA1 treatment decreased (p < 0.05) the total lipid content of liver compared to control at week 5 after calving. Our results show that CLA supplementation is more efficient in alleviating body mass mobilization and decreasing the incidence of subclinical ketosis when applied as early as 3 weeks before calving than started feeding after calving.

Effects of Geographical Accessibility on the Use of Outpatient Care Services: Quasi-Experimental Evidence from Panel Count Data

In 2010-2012, new outpatient service locations were established in Hungarian micro-regions, which had lacked such capacities before. We exploit this quasi-experiment to estimate the effect of geographical accessibility on outpatient case numbers using both individual-level and semi-aggregate panel data. We find a 24-27 per cent increase of case numbers as a result of the establishments. Our specialty-by-specialty estimates imply that a 1-min reduction of travel time to the nearest outpatient unit increases case numbers for example by 0.9 per cent in internal care and 3.1 per cent in rheumatology. The size of the new outpatient capacities has a separate effect, raising the possibility of the presence of supplier-induced demand. By combining a fixed-effects logit and a fixed-effects truncated Poisson estimator, we decompose the effects into increases in the probability of ever visiting a doctor on the one hand and an increase of the frequency of visits on the other hand. We find that new visits were dominant in the vast majority of specialties, whereas both margins were important for example in rheumatology. Finally, we demonstrate the usefulness of the fixed-effects truncated Poisson estimator in modelling count data by examining its robustness by simulations.

Influence of rumen-protected choline on liver composition and blood variables indicating energy balance in periparturient dairy cows

Rumen-protected choline (RPC) was evaluated for effects on the lipid and glycogen content of the liver and metabolic variables in the blood plasma of dairy cows. Thirty-two Holstein cows were allocated into two groups (RPC group with RPC supplementation and control group without RPC supplementation) 28 days before the expected calving. Cows were fed the experimental diet from 21 days before calving until day 60 of lactation. The diet of the RPC group was supplemented with 100 g/day of RPC from 21 days prepartum until calving and 200 g/day of RPC for 60 days postpartum, providing 25 and 50 g of choline, respectively. Liver samples were taken by percutaneous needle biopsy, then analysed for total lipid (TLl), triglyceride (TGl) and glycogen (GLYl) contents on days -21, +7, +35 and +60 relative to calving. Blood was collected on the same sampling days and 21 days after calving. Glucose, non-esterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), triglyceride (TGp), total cholesterol (TCh), urea, ammonia and aspartate aminotransferase (AST) were determined from blood samples. The TLl and TGl contents were 25.0 ± 4.3 g and 25.3 ± 3.8 g per kg wet weight (mean ± SEM), respectively, lower in the RPC group than in the control animals. No significant differences were observed in the GLYl concentrations between the two groups. However, a lower TGl: GLYl ratio was shown in the liver of cows fed the RPC diet as compared to the controls. RPC supplementation decreased BHBA while increasing TGp concentrations were shown in the blood of cows fed the RPC diet, possibly as a consequence of improved lipoprotein synthesis in, and triglyceride excretion from, the liver, together with a reduced rate of ketogenesis.

[Anterior cervical fusion on the lower cervical spine: own clinical experience]

Both acute and chronic instability of the cervical spine can be succesfully treated by anterior crevical fusion. The main goal is to create a spondylodesis through which the instable motion segments are fixed in the position defined by the surgeon. The spondylodesis is realised by the bone healing of the intervertebral space. The consolidation itself is facilitated by the operative stabilisation of the segments involved, and also by the implantation/transplantation of the osteoproductive/osteoinductive materials. The sooner consolidation is achieved, the more likely it is to be able to avoid the material dependent complications and/or that of dislocation. So as to support this theory a retrospective clinical/radiological study was performed. During this the length and the safety of the consolidation was measured by applying various anterior cervical plating systems. A total of 485 patients having cervical injuries or degenerative disc disease were treated by anterior cervical plating. For bone transplantation partly pure autolog spongious partly autolog cortico-spongious morsalised bone chips, furthermore autolog tricortical bone block were applied. A standard protocoll was used for data collection, evaluation and also follow-up. The patients treated with plate systems were divided into 3 groups: Group 1: Non-locked H-plate system with autogeneous cancellous bone (155 trauma patients, for a total of 210 cervical motion segments, 1.35 segments/patients). Group 2: Non-locked H-plate system with tricortical autograft (167 patients, for a total of 290 cervical motion segments, 1.73 segments/patients). Group 3: Locked cervical plate system with tricortical autograft (73 patients, for a total of 110 cervical motion segments, 1.5 segments/patients). Patients treated with standalone cage belong to group 4. These cages were filled with autogenous cortico-spongiosus bone chips (90 patients, for a total of 90 cervical motion segments, 1.0 segments/patients). Evaluations included postoperative clinical, X-ray and CT examination, and follow-ups at 6, 16, 52, and 104 weeks. We established three grades, and classified the degree of bony fusion between the graft and vertebra: not-yet-fused, fused or non-union. When evaluating the results the following statements/observations were made: a) There is a fast and safe consolidation in the case of those patients that underwent dinamic disc osteosynthesis (p = 0.00001). b) Whereas performing fixation with non-locked or locked screw plate systems and strutgrafted with tricortical autograft created prolonged healing requiring months and developed non-unions more often (non-locked screw-plate system versus locked screw-plate system) (p > 0.05). c) Using locked screw-plate fixation systems non-union rate in our study was 21%, suggesting that this form of fixation has only a limited use. d) In our study complete consolidation without pseudoarthrosis was achieved by using standalone cages filled with autolog cortico-spongiosus bone chips, but bony healing was delayed due to cage coating and the substitution of pure autogenous spongiosa for cortico-spongiosus bone chips. It is recommended to treat acute/chronic instability of the cervical spine both by using non-fixed plate system with autolog cancellosus bone and by standalone cage filled with cortico-spongiosus bone chips as well. It is worth keeping in mind that by applying this lattest an extra surgery to harvest the graft will be avoided.

Favorable Early Outcome of Carotid Artery Stenting Without Protection Devices

Background and Purpose— Protection devices are increasingly used in carotid artery stenting. However, no randomized trial has been conducted to evaluate the efficacy of such devices, and arguments have also been formulated against their routine use. We set out to investigate the complication rates associated with carotid artery stenting performed without protection devices. Applicability of covered stents in the carotid system was also evaluated.

Methods— Between January 2001 and July 2003, 245 consecutive patients (260 hemispheres) underwent carotid artery stenting. No protection devices were applied. Covered stents were implanted in 31 (12.1%) cases. The incidence of complications during the intervention and the subsequent 30-day follow-up period was recorded.

Results— The technical success rate was 98.8%. One postprocedural nonneurological death (0.4%) occurred. Neurological complications (inclusive of transient ischemic attacks) were observed in 14 cases (5.4%). The rate of major complications (death, major stroke, and myocardial infarction) was 1.6% among the symptomatic and 1.5% among the asymptomatic cases. The rate of minor strokes was 3.2% in the symptomatic and 1.5% in the asymptomatic group. Of the neurological complications, 64.3% occurred postprocedurally. No ipsilateral neurological complications were detected in the subgroup treated with covered stents.

Conclusions— Carotid artery stenting without protection devices appears to be safe. Most of the neurological complications could not have been prevented with protection devices, because they occurred after the intervention. The application of covered stents may reduce the rate of embolization-related complications in the periprocedural period.

[Lipomatous meningioma: report of two cases and review of the literature]

Lipomatous meningioma is a benign tumor characterized either by an admixture of mature adipocytes and meningioma or the production of triglycerides by neoplastic meningothelial cells assuming a lipoblast-like appearance. The authors report on two instances of this exceedingly rare lesion occurring in the left middle cranial fossa and over the right frontal convexity of two female patients aged 79 years and 60 years, respectively. In the former, the tumor was an incidental autopsy finding, while the latter underwent surgery for symptoms of intracranial space occupation. Light microscopy showed interwoven islands of fatty tissue and transitional meningioma in the first case; whereas a monomorphous signet-ring cell phenotype prevailed in the second. Oil-Red-O staining confirmed the presence of neutral fat in both specimens. Immunohistochemical coexpression of epithelial membrane antigen, vimentin, and S100 protein supported the meningothelial origin of tumor cells. On the other hand, the CD 68 macrophage antigen was not detected. Cytoplasmic lipid droplets along with hallmarks of meningothelial differentiation were visualized ultrastructurally in part of the meningioma component of the first case and throughout the second. These findings are consistent with a metaplastic origin of the adipocytic element. Whatever its histogenesis, lipomatous meningioma may, on occasion, represent a major challenge with therapeutic implications for both preoperative imaging and histological diagnosis.

The reaction of calves to helminth infection under natural grazing conditions. II. Pathology of terminal disease

Calves raised worm-free were exposed to natural infection on unimproved pasture infected with Trichostrongylus axei, Haemonchus placei, Ostertagia ostertagia, Cooperia punctata and C. pectinata, and Oesophagostomum radiatum. Some calves received, in addition, experimental infections of O. radiatum and H. placei. All calves showed depressed body weight gains. Haematocrit, haemoglobin, and serum protein levels were reduced, returned to normal after 15–18 weeks' grazing in calves that survived, but continued to fall and reached lower levels in those that died. Calves killed in extremis showed emaciation, oedema, degenerated fat tissue, inflammatory and degenerative changes in the gastrointestinal tract, and atrophy of the lymphatic tissues and thymus. These symptoms are reminiscent of a "wasting syndrome".

The histopathology of the reactions of calves to experimental infection with the nodular worm, Oesophagostomum radiatum (Rudolphi, 1803). II. Reaction of the susceptible host to infection with a single dose of larvae

The histopathological aspects of the host response to Oesophagostomum radiatum were studied in calves, reared worm-free, following a single dose of 5000–10,000 infective larvae. The penetration of larvae caused mainly productive changes in the gut tissue and was not followed by overt clinical symptoms. Five to seven days after infection, obliteration of small blood-vessels by endothelial proliferation and perivascular accumulation of histiocytes and lymphocytes occurred, \ particularly in the vicinity of the histotropic larvae, resembling a delayed type hypersensitivity reaction. The ensuing inflammation appeared to facilitate the termination of the histotropic phase by disorganizing the tissue produced around the third-stage larva during its development. The migration of fourth-stage larvae to the colon and subsequent moult to the fifth stage was accompanied by infiltration of eosinophil leucocytes into the gut tissue with accumulation of these cells around and within the mucosal glands, particularly in the colon. The resultant crypt abscessi, which resembled the active lesions found in ulcerative colitis, showed protracted healing, with formation of granulomas containing giant cells. Plasma cell production characteristic of a secondary response occurred only in the lymph nodes draining inflamed sections of the large intestine where adult worms were located. Healing of the acute enteritis resulted in fibrosis and hyperplasia of the gut wall.

The histopathology of the reactions of calves to experimental infection with the nodular worm, Oesophagostomum radiatum (Rudolphi, 1803). I. Host reaction to re-infection with single large doses of larvae

The histopathological aspects of the host response to Oesophagostomum radiatum were investigated following the reinfection of previously exposed calves. The elimination of third-stage larvae 18–22 hr after administration of the reinfecting dose was associated with oedema, hyperaemia, and hypersecretion in the intestine and was followed by a transient but intense diarrhoea. The infiltration of the oedematous intestinal tissues with eosinophil and neutrophil leucocytes and the vasculitis in the vicinity of the histotropic larvae indicated an Arthus type reaction. During the development of the third-stage larvae the exudative hyperergic inflammation changed to a proliferative granulomatous type. The moulting of the larva to the fourth stage was associated with a recurrence of oedema and vasculitis, and was followed by isolation and elimination of the larva and surrounding necrotic host tissue. If the larva was not discharged the healing was delayed and the nodular lesion persisted. The diarrhoea during the elimination of fourth-stage larvae was associated with oedema of the gut wall, hypertrophy, and profuse secretion of the mucosal glands. These changes developed to an excessive degree in the proximal 2 ft of the colon following the termination of the histotropic phase. The varying course of the enteric process was accompanied by simultaneous changes in the regional lymphatic tissue. Cell destruction, phagocytosis, and depletion of follicles during the acute phases alternated with lymphopoiesis during the proliferative reparative periods. The tissue damage from the exaggerated response to reinfection of a sensitized host resulted in anorexia and weight loss.

The reaction of calves to helminth infection under natural grazing conditions

The reaction to helminth infection was studied in calves grazing natural pasture in an area of south-eastern Queensland. Calves raised worm-free were exposed each month to natural infections with Cooperia punctata, C. pectinata, Trichostrongylus axei, Haemonchus placei, and Oesophagostomum radiatum. The observations extended over 2 years. Calves first exposed during the months of higher rainfall (December–April) suffered a mortality of 93%, whereas the mortality was 63% in those placed on the pasture during the drier months. Weight loss and death of calves during the first 8 weeks' grazing was associated with a pasture larval contamination of more than 50 larvae of the above species per sq yd. Evidence was obtained that O. radiatum was the main pathogen during the experimental period, and egg counts of this species greater than 380 eggs per gram of faeces were associated with clinical signs of infection. Some calves, which were initially exposed to infection shortly after seasonal rains had fallen, acquired the highest worm burdens and survived for less than 10 weeks. Calves which survived for 11–22 weeks were on a better than average pasture, and were first exposed to infection at least 4 weeks after suitable rains when the larval population had commenced to decline. These calves acquired approximately half the worm burden recorded for the calves which did not survive beyond 10 weeks. Calves surviving for longer than 22 weeks were first exposed to infection 2–3 months after seasonal rains, and showed a mean maximum O. radiatum egg count less than two-thirds of that recorded for the animals which survived for 11–22 weeks. Body weights in the group surviving for more than 22 weeks did not increase until after 20 weeks, when the egg counts had decreased to consistently low levels. Infective larvae of O. radiatum ingested after the first week did not contribute significantly to the adult population found at necropsy. Despite the inability of these larvae to complete their development, pathogenic effects of the continuous intake continued until about the 20th week. No evidence was found that the presence of haemagglutinating and complement fixing antibodies was correlated with the survival of calves.

Studies on resistance in calves to experimental infections with the nodular worm, Oesophagostomum radiatum (Rudolphi, 1803) Railliet, 1898

In calves reared free of Oesophagostomum radiatum and given a single infection of this helminth, the third ecdysis in the life cycle was completed in the gut wall in 5-7 days. The fourth stage larva moved into the gut lumen between the seventh md 14th days, where the fourth ecdysis occurred between 17 and 22 days. The prepatent period was 32-42 days. Egg production reached its peak usually during the sixth to 10th weeks, and in most calves this rate of production persisted for only 1-4 weeks. The subsequent decline in the egg count to low levels was very rapid, and was accompanied by the elimination of most of the adult worms. Reinfection with large doses of larvae, either during the period of peak egg production or some weeks later when the egg count was at low levels, did not produce any increase in the egg count, except on rare occasions. In these instances only a small increase was detected. Egg counts of calves given daily doses of larvae showed a trend similar to that resulting from a single dose, and attempts at reinfection with massive doses when the egg count had declined to low levels were also unsuccessful in producing any appreciable rise in the egg count. The failure of the egg count to respond to a challenge dose of larvae is regarded as evidence that a resistance to reinfection had been acquired. Resistance was apparent following a single dose as low as 1000 larvae and a daiIy dose as low as 50 larvae. Necropsies confirmed this conclusion and indicated that, whereas the host resistance mechanism could be responsible for the encapsulation of some reinfecting larvae in the gut tissues and their subsequent death, such mechanism was directed mainly against fourth stage larvae shortly after they had moved back to the gut lumen. The reaction here resulted in the elimination of all or most of the larvae and was accompanied by diarrhoea. While some reinfecting larvae survived in nodules for many weeks in the third or fourth stage, it would seem that the majority of those successfully penetrating the tissues completed the histotrophic phase within the normal period. The few reinfecting larvae which survived to maturity in the gut lumen completed their development also within the normal period. Infection was followed by the production of circulating antibodies detectable by both the haemagglutination and complement fixation tests. With calves infected with a single dose of larvae, all developed haemagglutinins, but complement-fixing (C. F.) antibodies were detected only in some, and these had become infected with Cooperia spp. prior to the experiment. Levels of both types of antibody were low, only exceeding in a few calves a titre of 1/80 for haemagglutinins and of 1/20 for C. F. antibodies. Following reinfection, C. F. antibodies were detected in all animals. They appeared simultaneously with haemagglutinins and there was little evidence that reinfection had stimulated any significant secondary rise in either type of antibody. The available data gave no definite indication of any effect of these antibodies in host-parasite reactions. They suggest, however, that haemagglutinins may be indicative merely of a state of infection, and that C.F. antibodies are stimulated more readily after reinfection.