Acute lower respiratory tract infections in children in Kuwait.

The features of community-acquired acute lower respiratory tract infections in 390 children are described. Half (50%) presented with bronchiolitis, 37% with pneumonia and 13% with croup. Respiratory syncytial virus was the commonest agent identified (52% of bronchiolitis, 29% of pneumonia, 51% of croup). Positive bacterial blood cultures were obtained in 10% of the patients, all except one with pneumonia. Fever (> 39 degrees C), a toxic ill look, bronchial breathing, WCC > 20 x 10(9)/l, neutrophils > 5 x 10(9)/l, platelet count > 500 x 10(9)/l, ESR > 45 mm/hr, lobar consolidation and pleural effusion were more likely to be associated with bacterial than with viral pneumonia (relative risk > 1.81; p < 0.05). In areas with limited resources, a high fever, a toxic ill look, bronchial breathing and simple laboratory tests may help to identify patients with bacterial pneumonia.

Laboratory diagnosis of acute lower respiratory tract viral infections in children.

This report summarizes and compares the results of complement fixation test (CFT), virus isolation (VI), and direct immunofluorescence test (DIF) for the antigen detection of respiratory syncytial virus (RSV), influenza A virus (Flu A), and adenovirus in 62 children with acute lower respiratory tract infections (ALRI) in Kuwait. It includes, as well, CFT results for parainfluenza virus and Mycoplasma pneumoniae. Combining the three methods, a potential causative agent was identified in 56 (90 per cent) children, of whom 14 (22 per cent) had evidence of infection with more than one pathogen. RSV was most frequently identified followed by Flu A, parainfluenza, Mycoplasma pneumoniae and adenovirus. Virus isolation proved the best method for identification of RSV, Flu A, and adenovirus [identified 52 (84 per cent) cases]. DIF was sensitive for RSV detection (sensitivity 84 per cent, specificity 94 per cent), and less sensitive for Flu A (sensitivity 62 per cent, specificity 98 per cent). However, DIF was completely insensitive to adenovirus (no positives). CFT was positive for the five pathogens in 44 (71 per cent) of the population studied; therefore, almost 20 per cent of positive identifications would have been missed if VI and DIF were not done. The sensitivity and specificity of CFT for RSV, adenovirus and Flu A were 71, 75, and 31 per cent, and 94, 96, and 94 per cent, respectively. Based on the results of this pilot study, it appears that a combination of the three tests yields the best rate of virus detection. Cell culture cannot be discarded for the identification of some respiratory viruses, especially adenovirus, until better techniques, or more sensitive reagents are applied. However, since RSV is the virus most commonly involved in children with ALRI, we recommend using DIF on routine basis for diagnosis. Its results compare well with virus isolation; it is simple, rapid, and inexpensive.

Residue analysis of DDT, malathion and kelthane on pears.

Malthion, DDT, kelthane and their mixture (3 : 10 : 5) were applied to pear fruits at the rate recommended by the Ministry of Agriculture. The rate of disappearance of their residues on pear fruits was investigated under refrigerated conditions (2 +/- 1 degree and 47% relative humidity (RH)). The same insecticides were tested in higher concentrations (1.5 and 2 times) to determine the effect of insecticides on the black spots usually found on pears after storage. No relation was found between the tested insecticides and the appearance of the black spots. Residue-disappearance curves of the three tested concentrations of these insecticides and their mixture were drawn on semi-log paper. The residues of each material found on pear fruits after one hour, 1, 8, 15, 30 and 45 days' storage in a refrigerator, estimated biologically by C. pipiens larvae and D. magna were recorded. The highest concentrations of the mixture and of the individual insecticides left higher residues on pears than the lower ones of all the insecticides either as a mixture or alone. Stored pears, refrigerated under the above conditions immediately after treatment with the mixture of insecticides recommended for the pest control of pears, cannot be consumed fresh after 45 days.

Standard curves for nuvacron, malathion, sevin, DDT and kelthane tested against the mosquito Culex pipiens L. and the microcrustacean Daphnia magna Straus.

The fourth instar larvae of Culex pipiens L. and adults of microcrustacean Daphnia magna Straus were reared under standardized conditions and used as bioassay test organisms for the preparation of the standard log concentration--probit (lc--p) regression lines for each of the following pesticides: nuvacron, malathion, sevin, DDT and kelthane. When the above pesticides were tested against the larvae of C. pipiens, the LC50 values (in ppm) ranged as follows: nuvacron 0.0014--0.0019, malathion 0.0027-0.0043, sevin 0.059-0.095, DDT 0.233-0.525, kelthane 0.17-0.24 and a mixture of malathion, DDT and kelthane (3 : 10 : 5) 0.1805-0.2451, based on 24-h readings. The corresponding LC50 values (in ppm) for D. magna were 0.00018-0.00032, 0.000074-0.00013, 0.00063-0.00069, 0.0061-0.0064, 0.071-0.090 and 0.055-0.028 for the aforementioned pesticides. D. magna proved to be more sensitive to all tested pesticides than C. pipiens larvae: it succumbed to concentrations ranging from 0.000032 to 0.004 ppm of nuvacron, from 0.000032 to 0.0016 ppm of malathion, from 0.000032 to 0.02 ppm of sevin, from 0.0008 to 0.1 ppm of DDT, from 0.03 to 0.3 ppm of kelthane and from 0.007 to 0.075 ppm of the mixture. C. pipiens larvae were affected by concentrations ranging from 0.0005 to 0.008 ppm of of nuvacron, from 0.0005 to 0.04 ppm of malathion, from 0.008 to 1.0 ppm of sevin, from 0.05 to 2.5 ppm of DDT, from 0.06 to 0.5 ppm of kelthane and from 0.07 to 0.75 ppm of the mixture.

Effects of plant species, age and part on the disappearance of sevin, nuvacron and malathion residues.

Residues as determined by bioassay using Daphnia or mosquito larvae were in agreement with each other in most cases except sevin residues at 1 h and 8 days after treatment of mallow. The mosquito larvae failed to record nuvacron, sevin and malathion on 45-day-old plants on the 8th, 12th and 24th day, respectively, whereas residues on younger plants continued to affect mosquitoes up to the 12th day and disappeared only on the 24th day. Daphnia continued to show toxicity up to the 24th day on younger and older plants. Insecticide residues of nuvacron, malathion and sevin, found on the leaves 30- and 45-day-old plants of cotton, Jew's mallow and kidney beans after 1 h, 1, 4, 8, 12 and 24 days were estimated biologically by C. pipiens larvae and D. magna. Residues of insecticides disappeared more readily on bean pods than on bean leaves. Residues of sevin, malathion and nuvacron found on the pods 12 days after treatment as indicated by Daphnia were 0.189, 0.055 and 0.059 ppm respectively. They are far less than the corresponding residues on bean leaves. The 1-hour residue was higher on younger bean leaves than on mallow and cotton with very few exceptions (nuvacron, malathion and sevin: 2.125, 11.75 and 95 ppm on cotton leaves; 2.25 and 145 ppm on Jew's mallow and 3.750, 32.500 and 250 ppm on common bean leaves, respectively). These data were obtained with C. pipiens larvae. The picture was completely reversed on 45-day-old plants. 1-h deposits of malathion were higher on mallow than on cotton or beans (nuvacron, malathion and sevin; 2.3, 200 and 140 ppm on cotton leaves, 1.90, 191.15 and 92.86 ppm on mallow leaves, 2.25, 21.5 and 137.5 ppm on common bean leaves, respectively). These data were obtained with C. pipiens larvae. Nuvacron residues on 45-day-old mallow were less on mallow than on cotton or beans. Sevin was higher in 1-h residues on cotton and beans than on mallow. Mallow did not retain insecticides as long as did cotton and beans. The initial concentration of nuvacron was little less than that of sevin and malathion. It was more toxic to mosquito larva (LC50 = 0.0016 ppm) than malathion (LC50 = 0.0034 ppm) and sevin (LC50 = 0.075 ppm). Daphnia was more affected by malathion (LC50 = 0.000098 ppm) than by nuvacron (LC50 = 0.00024 ppm). Nuvacron was nearly equitoxic to sevin (LC50 = 0.00026 ppm) against Daphnia. In spite of this all tested plants, both young or older ones, retained nuvacron in the smallest quantities in proportion to the other insecticides. The 1-h residues were less on older plants (except cotton) for only nuvacron and sevin: 2 and 94.5, 1.9 and 92.8 ppm than on younger ones 2.4 and 137.2, 2.25 and 145 ppm as indicated by Daphnia and mosquito larvae respectively. This emphasizes that the initial concentration is not the limiting factor for the determination of the 1-h residue as the initial concentration was much higher on older than on younger plants.