Exploratory space-time analysis of dengue incidence in Trinidad: a retrospective study, 1998-2004

OBJECTIVE: To obtain an understanding of the space and time dynamics of dengue and provide health agencies with important clues for reducing its impact. DESIGN AND METHODS: Dengue Haemorrhagic Fever (DHF) cases observed for the period 1998-2004 were georeferenced using Geographic Information System software. Spatial clustering was calculated for individual years and for the entire study period using the Nearest Neighbor Index. Space and time interaction between DHF cases was determined using the Knox Test while the Nearest Neighbor Hierarchical method was used to extract DHF hot spots. All space and time distances calculated were validated using the Pearson r significance test. RESULTS: Results shows that (1) a decrease in mean distance between DHF cases correlates with activity leading up to an outbreak, (2) a decrease in temporal distance between DHF cases leads to increased geographic spread of the disease, with an outbreak occurrence about every 2 years, and (3) a general pattern in the movement of dengue incidents from more rural to urban settings leading up to an outbreak with hotspot areas associated with transportation hubs. CONCLUSION: The results of this study can be used by public health officers to help visualize and understand the spatial and temporal patterns of dengue, and to prepare warnings for the public. Dengue space-time patterns and hotspot detection will provide useful information to support public health officers in their efforts to control and predict dengue spread over critical hotspots allowing better allocation of resources.

Potassium channel openers exhibit cross-tolerance with morphine in two experimental models of pain.

OBJECTIVE: The study was performed to assess the effect of potassium channel openers on morphine tolerance and vice-versa. METHODS: Swiss albino mice of either gender weighing between 25-30 g were used for the study The study assesses the effect of potassium channel openers (cromakalim, diazoxide and minoxidil) on morphine tolerance and vice-versa, using formalin and tail-flick tests. RESULTS: The antinociceptive effect of cromakalim and minoxidil was significantly reduced when administered to morphine-tolerant mice, in both the behavioural tests. However reduced analgesic effect of diazoxide was observed on morphine-tolerance in the formalin test but not in the tail-flick test. Tolerance was observed when morphine was administered to animals chronically treated with any of the potassium channel openers. The same effect was observed when morphine was injected into a group treated with a combination of morphine and any of the potassium channel openers. CONCLUSIONS: This study, therefore, suggests that both morphine and potassium channel openers are cross-tolerant. However such interaction occurs at the level of potassium channels rather than at the level of receptors.

Inoculation injuries in hospitals in Trinidad and Tobago.

This paper reviews the frequency of inoculation injuries, which occurred in hospitals in Trinidad and Tobago from 1991 to 1997, inclusive. A total of 397 cases of inoculation injuries were detected. Significantly more of these injuries occurred during diagnostic or therapeutic procedures (231, or 58.2%; G = 41.2, df 9, p < 0.001) than during disposal of needles and other sharps (136, or 34.3%), certain situations remote from patient care (21, or 5.2%), and 'rogue incidents' related to unsafe disposal with later injury to janitors or others (9, or 2.3%). No statistically significant monthly or seasonal variations occurred in the incidence of reported inoculation injuries. The two institutions that saw the largest number of patients, the Port-of-Spain General and San Fernando General Hospitals, accounted for the largest number of cases of inoculation injury, with 139 (35.0%) and 135 (34.0%), respectively. Interestingly enough, there were 42 reported inoculation incidents at the St. Ann's Hospital for the Mentally Impaired and 23 (52.5%) of these were bites, most of them occurring during attempted procedures. Nurses were the main recipients of inoculation injuries (287 cases, or > 72%), followed by doctors (9.3%), and ward maids (6.2%). The main modes of inoculation were needle sticks (305, or 76.8%). Bites (34, 8.6%), injuries with sharps other than needles (29, or 7.3%), and splashes (29, or 7.3%) were the other types seen. One recipient was found to be infected with HIV following accidental inoculation. The infection control methodologies used in hospitals in Trinidad and Tobago are reviewed and recommendations for preventing injuries are outlined.

Lymph nodes in leprosy

1- Clinically 155 acses of leprosy were examined for enlargement of lymph nodes, and or several showed definite enlargement in 95 cases. 2- In order of frequency the enlarged nodes were: epitrochlear (62 per cent), inguinal (45 per cent), cervical (33 per cent) and axillary (20 per cent). 3- There was no correlation between the site of cutaneous lesion and the regional lymph node enlargement. 4- Biopsies were made of 40 lymph nodes; 24 from lepromatous cases (2 of them mixed), and 16 from tuberculoid cases. 5- Characteristic lepromatous infiltration of the nodes was found in all the specimens from the lepromatous cases. 6- Peripheral sinuses were involved only in 3 instances, whereas intermediary sinuses were packed with typical Virchow lepra cells in almost all of the nodes from lepromatous cases. 8- The reticulin framework in areas of lepromatous infiltration was well preserved. 9-Thickening of capsule, periadenitis, and patches of fibrosis were seen only in very few cases. 10- Sixteen lymph nodes from tuberculoid leprosy did not show any histological alteration from normal.