Asoke K. Basu

Characterization of Giardia duodenalis infections in dogs in Trinidad and Tobago

To our knowledge, the zoonotic potential of Giardia duodenalis has not been assessed in companion animals in Trinidad and Tobago. This report details the first attempt to evaluate the potential zoonotic risk of G. duodenalis in dogs and identify assemblages of G. duodenalis found in dog populations on both islands. Fecal samples were collected from free-roaming dogs and dogs at the Trinidad and Tobago Society for the Prevention of Cruelty to Animals from October 2010 to June 2011. A total of 168 samples were collected of which 104 samples were analyzed for the presence of G. duodenalis by PCR amplification of the ssu-rRNA gene with subsequent assemblage-typing. A subset of samples was also analyzed by ELISA. Twenty-six samples were positive for G. duodenalis by PCR for an overall prevalence of 25%. Four samples were identified as assemblage C (15.4%), 21 as assemblage D (80.8%), and one as assemblage E (3.8%). Puppies were four-times more likely to be infected with G. duodenalis than adult dogs (OR 4.61, 95% CI 1.73-12.2). There was a significant agreement between ELISA and PCR in the detection of the protozoa (κ=0.67). We infer from our results that while the prevalence of G. duodenalis is relatively high in Trinidad and Tobago, the zoonotic risk of infection in humans is low since neither assemblage A nor B was identified in the study population.

Efficacy of commonly used anthelmintics: First report of multiple drug resistance in gastrointestinal nematodes of sheep in Trinidad

In Trinidad, small ruminant farms are semi-intensively managed under tropical conditions which support the development and survival of the infective stages of the helminths. Local farmers use anthelmintics to control gastrointestinal nematodes frequently. Frequent use of anthelmintics has the potential to select for populations of nematodes resistance to those chemicals. Hence, an attempt was made to study the efficacy of commonly used drugs on gastrointestinal nematodes of sheep. Three farms situated in different counties in Trinidad were selected. Sheep aged 6-15 months and not treated with anthelmintics for a minimum of six months previous and with faecal egg count (FEC)>150 eggs per gram were selected for study. They were allocated into 5 groups, each consisting 10 animals. The Group TA animals were treated once with albendazole (5mg/kg. b.wt.), group TF with fenbendazole (5mg/kg.b.wt.), group TI animals with ivermectin (200 μg/kg b.wt.), group TL with levamisol (7.5mg/kg b.wt.). The group NTC animals were not given any drug and served as control. The number of nematode eggs per gram of faeces from each animal was determined before treatment and at 14 days after treatment. The anthelmintic susceptibility to different drugs was detected by FECRT (in vivo) with EPG recorded at 14 day post-treatment. The data analysis using FECRT revealed that efficacy of albendazole (46-62%), fenbendazole (44-61%) and levamisol (53-81%) were reduced compared to ivermectin (95-97%). An attempt has also been made to find a suitable method for calculation of FECR (%).

Prospective study investigating transplacental transmission of equine piroplasmosis in thoroughbred foals in Trinidad

Equine piroplasmosis caused by Theileria equi and Babesia caballi is endemic in Trinidad and Tobago. Transmission occurs by ticks of the family Ixodidae. T. equi can also be transmitted transplacentally; however transplacental transmission of B. caballi is unknown. This study aims to investigate transplacental transmission of equine piroplasmosis from thoroughbred mares naturally infected via the tick vector. Whole blood and serum samples were collected from 117 mares in the fifth month of pregnancy. Blood samples were also collected from each of their foals (89 in total) within the first 36h of birth. Additionally, all foals were observed for clinical signs within 30days post - partum. All samples were examined microscopically for intra-erythrocytic piroplasms. Serum ELISA tests and PCR analysis on whole blood were performed to determine the presence of T. equi and B. caballi. Thirty-four (30.6%) mares and 14 (15.7%) of their foals were seropositive for T. equi. Twenty-seven (24.3%) mares were positive for T. equi by conventional (c) PCR. Real time (q) PCR analysis based on the ema - 1 gene revealed that seven (8%) foals were positive for T. equi. Eighty-nine (76.1%) mares and 38 (42.7%) foals were seropositive for B. caballi. Four (3.4%) mares were positive for B. caballi by cPCR. Three out of the four cPCR positive mares either had resorptions, or stillbirths for that pregnancy. From this study, there is strong evidence that transplacental transmission of B. caballi can occur leading to foetal losses. Six foals (7%) were positive for B. caballi by qPCR. Of these six, four were born to B. caballi seropositive mares. In this study a foal born of a T. equi seropositive mare was 55.7 times more likely to be serologically positive for T. equi than a foal born to a T. equi seronegative mare. Similarly a foal born of a B. caballi seropositive mare was 39.4 times more likely to be serologically positive for B. caballi than a foal born to a mare that was serologically negative for B. caballi at the fifth month of pregnancy. This is as a result of the ingestion of colostrum containing antibodies to these pathogens. Mares should be screened during pregnancy and their foals closely monitored at parturition for evidence of equine piroplasmosis so that treatment can be implemented earlier for a better prognosis.

A General Account of Ticks

Ticks are arthropods belonging to the Class Arachnida. They can be further classified as hard ticks (suborder Ixodida) or soft ticks (suborder Argasidae). Both suborders are very important in veterinary and human medicine since they are implicated in disease transmission due to the spread of tick-borne pathogens, cause physical damage to their hosts and in some instances death. Ticks are responsible for billions of dollars in losses in the livestock industry worldwide due to the impact of the pathogens they spread to susceptible hosts. To date there are over 900 tick species.

Tick Species Present in Trinidad and Tobago

The report, based on the review of literature of more than the past 10 decades, revealed a total of 23 tick species present in Trinidad and Tobago, with a greater number of species on the island of Trinidad. The tick genera found in these twin islands include Argas, Ornithodoros, Amblyomma, Dermacentor, Haemaphysalis, Ixodes , and Rhipicephalus . These tick species parasitize humans, wild and domestic animals. In addition to humans, hosts include mammals like bats, equids, ruminants, rodents and marsupials, birds including fowls, amphibians like toads and a variety of reptiles such as tortoises and snakes. Based on geographical location, most of the tick species found in Trinidad and Tobago have also been recorded in other parts of the Caribbean region, North, Central and South America. Soft and hard ticks found in Trinidad and Tobago have been reported to transmit a number of blood-borne pathogens including Borrelia, Ehrlichia, Babesia, Hepatozoon, Rickettsia , and Anaplasma .