Successful treatment of severe form of bovine tropical theileriosis in dairy cattle and genotyping of Theileria annulata isolates of Tamil Nadu, India.

Bovine tropical theileriosis (BTT) is a tick-borne protozoan disease of cattle and responsible for major economic losses to the dairy farmers in India. This report describes diagnosis, genotyping and successful treatment of heavy infection of Theileria annulata in an organized dairy farm at Kattupakkam, Chennai. Four cross bred cows of 2 to 5 years of age showed clinical signs i.e., anorexia, salivation and panting. Clinical examination revealed pyrexia (40.0 °C to 40.1 °C), pale mucus membranes, enlarged prescapular lymph nodes and haemoglobinuria. The peripheral blood smear examination of infected cows revealed presence of piroplasm within the RBCs indicating high parasitemia. Haematology results suggested that decreased levels of Hb, RBC, WBC and PCV in the infected cows when compared with normal reference values. There were increased serum ALT and AST values and reduced serum total protein, albumin, calcium and phosphorous values in the infected cows. Semi-nested PCR using T. annulata specific oligonucleotide primers amplified 199 bp of the partial T. annulata 18S rRNA gene. Presence of four satellite markers TS6, TS8, TS9, and TS12 in the Theileria annulata isolates 1 and 2 indicating that the isolates were the same haplotype and suggested the infection in the farm was due to a single haplotype of T. annulata parasite. Based on the clinical signs, microscopic examination of blood smear and molecular diagnosis, the condition was diagnosed as tropical theileriosis. Infected cows were successfully treated with a single deep intramuscular injection of buparvaquone (Zubion®, INTAS pharmaceuticals LTD, Ahmedabad, India) along with supportive medication.

Evaluation of cross-protection between O1 Manisa and O1 Campos in cattle vaccinated with foot-and-mouth disease virus vaccine incorporating different payloads of inactivated O1 Manisa antigen.

Serology is used to predict vaccine induced protection against challenge with a heterologous strain of the same serotype of foot-and-mouth disease virus (FMDV). To evaluate the accuracy of such predictions, we compared the protection afforded to cattle vaccinated with the O(1) Manisa strain of FMDV against challenge with either a homologous (O(1) Manisa) or a heterologous strain (O(1) Campos). Serology by virus neutralization test (VNT) using O(1) Manisa antiserum predicted an acceptable protection against such a challenge. Two experiments were carried out to compare the results for consistency. A total of 78 naïve cattle were vaccinated with different antigen payloads (60-0.94 µg) of O(1) Manisa. They were challenged by intradermolingual inoculation with live FMDV, either O(1) Manisa or O(1) Campos. Unvaccinated naïve control cattle (n=20) were also challenged with either the O(1) Manisa or O(1) Campos viruses and all developed generalized FMD. The protection results for the vaccinated cattle revealed that higher payloads of O(1) Manisa vaccine were needed to protect against heterologous challenge compared to that for homologous challenge. The 50% protective dose (PD(50)) values for the vaccine in experiments 1 and 2 were found to be 28.78 and 9.44 for the homologous challenge and 3.98 and 5.01 for heterologous challenge. Furthermore, protection against O(1) Campos required a higher level of vaccine-induced antibody against this virus compared to the level of O(1) Manisa neutralizing antibody associated with protection against homologous challenge. The 50% protective level of in vitro neutralizing antibody was found to be log(10)1.827 for O(1) Campos and log(10)0.954 for O(1) Manisa based on O(1) Manisa based virus neutralization test.

Protection against direct in-contact challenge following foot-and-mouth disease vaccination in sheep and goats: the effect on virus excretion and carrier status.

The ability of foot-and-mouth disease (FMD) vaccine to protect sheep and goats from a homologous direct in-contact challenge and the effect on virus excretion from the nasal secretions and oropharynx was examined. An experimental oil adjuvant O(1) Manisa FMD vaccine protected sheep and goats from clinical disease from 7 days post vaccination following 24 hours of direct in-contact exposure to four infected donor sheep or goats. Goats required lower antibody titres for protection when compared with sheep. Protection from clinical disease did not prevent localized viral replication in goats and at least two goats had viral RNA detected on day 28 post challenge. Quantitative reverse transcriptase polymerase chain reaction showed that the level of virus replication shortly after direct in-contact challenge in oropharynx and nasal secretions of vaccinated animals was reduced by 100 and 1000 times respectively when compared with unvaccinated controls. The findings also show that after direct in-contact challenge, use of FMD vaccine will prevent or reduce local virus replication, thereby significantly reduce the amount of virus released into the environment in the all-important early post-exposure period. There is low risk of vaccinated animals transmitting disease as live virus could not be readily isolated.

Effect of FMD vaccine antigen payload on protection, sub-clinical infection and persistence following needle challenge in sheep.

The relationship of Foot-and-Mouth Disease (FMD) virus antigen payload and single and double vaccinations in conferring protection against virus challenge in sheep was studied. Sheep vaccinated with half the cattle dose (1 ml) containing 15 and 3.75 µg of FMDV antigen with or without booster resisted virulent challenge on 21 days post vaccination or 7 days post booster. FMDV RNA could be detected in nasal secretions in 26% of vaccinated sheep (10(3.12) to 10(3.82) viral RNA copies) on day 35 post challenge. No live virus could be isolated after 5 days post challenge indicating that the risk of transmission of disease was probably very low. The finding showed that vaccines containing antigen payload of 1.88 µg may prevent or reduce the local virus replication at the oropharynx and shedding of virus from nasal secretions and thereby reduce the amount of virus released into the environment subsequent to exposure to live virus. Sheep with no vaccination or with poor sero conversion to vaccination can be infected without overt clinical signs and became carriers.